TCP MSS

Hi Experts

Greetings!

What is the default MSS size defined in cisco IOS to host TCP communication, I saw the package snipper output that the MSS is defined to 536 even if the MTU of the link is 1500. Why cisco IOS does not 1460 [header (20 + 20) to throw TCP IP &] as the default MSS for TCP communication and what is the purpose of choosing a minimum value of MSS 536 by deafult?

Thanks in advance

Bava -.

 There have been some assumptions made about using other than the
   default size for datagrams with some unfortunate results.

      HOSTS MUST NOT SEND DATAGRAMS LARGER THAN 576 OCTETS UNLESS THEY
      HAVE SPECIFIC KNOWLEDGE THAT THE DESTINATION HOST IS PREPARED TO
      ACCEPT LARGER DATAGRAMS.

         This is a long established rule.

   To resolve the ambiguity in the TCP Maximum Segment Size option
   definition the following rule is established:

      THE TCP MAXIMUM SEGMENT SIZE IS THE IP MAXIMUM DATAGRAM SIZE MINUS
      FORTY.

         The default IP Maximum Datagram Size is 576.
         The default TCP Maximum Segment Size is 536.

https://Tools.ietf.org/html/rfc879

Tags: Cisco Network

Similar Questions

Problem with multiple downloads with the router. Allows you to change the TCP MSS value?

Original title: TCP MSS

Hi all.

I currently have a problem with multiple downloads with my current router. If I have two current downloads at the same time I have no access to all web sites. It's almost as if the downloads take my meaning of bandwidth there is more nothing for ordinary surfing.

As a test I put an older router on my system and have a significant improvement in performance. I have 2 downloads in progress and also surf at the same time.

To compare two routers, I noticed that the only real difference between the two is that the TCP MSS value is set to '0' on the router of the problem, and then assign him 1392 (MTU - 40) on the router to elderly who gives better performance.

It is my understanding that this value governs the size of transmitted packets.

My question is this:

What is the MSS value which is causing the problem?

Congratulations in advance.

Be sure to interpret the values. The '0' means no not literally because the link would not work. It is likely, that it allows the local device set limits for the link. Don't forget that there is a Maximum value and as such can be any value up to such limit as defined by all devices in the path.

You can try capping manually but it is unlikely that any local limit will come to effect unless you set very low.

TCP MSS adjust

Hi all.

every once in awhile, I submit my show run-config for WLCCA (405beta).

I was alerted to the fact that each access point on my network as a different size of MSS 'best practices '. The message was this:

It is recommended to set the MSS size to 1300

I've been reading around and the best practice is to set the size of the TCP MSS AP of 1363.

Although not quite sure which is the correct value.

See you soon.

Same I used some tos and 1363 but according to this doc:

https://supportforums.Cisco.com/discussion/12561151/new-wlcca-40-open-be...

his recommaned put in 1300.

Concerning

Remember messages useful rates

Packet switching not EFC / what is 'classification of output EAC?

Hello

I noticed a 3945-DRY with fairly high CPU load without doing much, because there are more packages switching process that the CFR switched.

To study, I did the following:

Router #sh ip cef switching statistics feature

Input characteristics IPv4 CEF:

Feature road Drop consume Punt Punt2Host gave

Access the list 24911921 0 0 14678240 0

0 0 0 0 20433673 routing policy

24911921 0 0 14678240 20433673 total

Output features IPv4 CEF:

Feature Drop consume Punt Punt2Host new i / f

Class output EAC 715266717 0 0 0 0

Total 0 0 715266717 0 0

Characteristics of post-encap IPv4 CEF:

Feature Drop consume Punt Punt2Host new i / f

IPSEC Post-encap 1 655816389 0 0 0

Total 1 655816389 0 0 0

CEF IPv4 for us offers:

Feature Drop consume Punt Punt2Host new i / f

Total                            0          0          0          0          0

Features of punt IPv4 CEF:

Feature Drop consume Punt Punt2Host new i / f

Total                            0          0          0          0          0

Features local IPv4 CEF:

Feature road Drop consume Punt Punt2Host gave

Total                            0          0          0          0          0

Punted them (= "punted" another mechanism of switching, not switched cef) packages for the feature 'EAC exit class' increase of ~ 1000 per second.

This made me wonder, what exactly is the feature 'CEC output class'. As I can see in the following output, this feature is enabled on my Tunnel Interface:

Router ip int tu0 #sh

Tunnel0 is up, line protocol is up

The Internet address is x.x.x.x/xx

Broadcast address is x.x.x.x

Address determined by non-volatile memory

MTU is 1400 bytes

Support address is not set

Transfer of directed broadcast is disabled

Multicast reserved joined groups: 224.0.0.10

Outgoing access list is not defined

Inbound access list is not defined

Proxy ARP is disabled

Local Proxy ARP is disabled

Security level is default

Split horizon is enabled

ICMP redirects are never sent

ICMP unreachable is always sent

Mask the ICMP responses are never sent

IP fast switching is enabled

Fast on the same switching interface IP is disabled

IP stream switching is disabled

IP CEF switching is enabled

Vector turbo IP CEF switching

Turbo IP vector draw

Tunnel VPN routing/Forwarding "xxx".

Quick change IP multicast is enabled

Fast switching of distributed IP multicast is disabled

Flags of IP route cache is fast, CEF

Router discovery is disabled

Output IP packet accounting is disabled

Accounting of IP access violation is disabled

TCP/IP header compression is disabled

RTP/IP header compression is disabled

Policy routing is disabled

Network address translation is disabled

BGP policy mapping is disabled

Input characteristics: process Packet Capture, check MCI, TCP adjust MSS

Characteristics of the output: classification of output of EAC, PNDH redirect, adjust EAC ranking NAT, TCP MSS, QoS preclassification

Display the characteristics of encapsulation: IPSEC Post-encap output classification

WCCP redirect outgoing is disabled

WCCP redirect incoming is disabled

WCCP redirect exclude is disabled

Someone tell me, what is "CCE output ranking" and why this is receptive used by my router?

Hello Sebastian,.

EAC is the engine of common classification. I think that its used to "match" traffic for features like qos, nat, etc.. ". Based on the "HS in you ' out, some features on the direction of the output are originally be punted packets. You can try "debug ip cef drop" for a few seconds while the meter is incremented, usually it will give a reason to punt. The most common reasons are listed below.

ACL log or log-entry option (or)

An unreachable next hop for a route (or)

A missing arp entry for a next jump (or)

Entry to arp for outside nat... etc.

Please rate this post without fault if you found it useful. *

Thank you best regards &,.

Vignesh R P

ACCESS LIST QUESTIONS?

I have a hand router Cisco 871 and 5 remote sites using the Cisco 850. The tunnel comes up fine and can ping back from the 850 to the 871. However, I think that I have a problem of access list because I can't open the main database which is on the main site of any of the 5 locations nor do I get on the internet that the proxy server get no not at other sites. I can ping these remote sites, but cannot use them in fact. These rules are very different, and then the PIX.

192.168.1x

* THE REMOTE SITE

access-list 100 permit ip 192.168.1.0 0.0.0.255 192.168.0.0 0.0.0.255

access-list 101 deny ip 192.168.1.0 0.0.0.255 192.168.0.0 0.0.0.255

access-list 101 permit ip 192.168.1.0 0.0.0.255 any

not run cdp

sheep allowed 10 route map

corresponds to the IP 101

192.168.0.X

HAND ROUTER

recording of debug trap

access-list 100 permit ip 192.168.0.0 0.0.0.255 192.168.1.0 0.0.0.255

access-list 101 deny ip 192.168.0.0 0.0.0.255 192.168.1.0 0.0.0.255

access-list 101 deny ip 192.168.0.0 0.0.0.255 192.168.6.0 0.0.0.255

access-list 101 deny ip 192.168.0.0 0.0.0.255 192.168.7.0 0.0.0.255

access-list 101 deny ip 192.168.0.0 0.0.0.255 192.168.5.0 0.0.0.255

access-list 101 permit ip 192.168.0.0 0.0.0.255 any

access-list 102 permit ip 192.168.0.0 0.0.0.255 192.168.6.0 0.0.0.255

access-list 103 allow ip 192.168.0.0 0.0.0.255 192.168.7.0 0.0.0.255

access-list 104. allow ip 192.168.0.0 0.0.0.255 192.168.5.0 0.0.0.255

not run cdp

sheep allowed 10 route map

corresponds to the IP 101

!

IP tcp mss<68-10000>

Hope this helps,

Gilbert

Size of df ping 1400-failed

Hello

I tried to ping with mtu size 1400 via VPN tunnel in vain.

Size of Kim #ping 192.168.2.1 df 1400

Send 5, 1400-byte ICMP echoes 192.168.2.1, time-out is 2 seconds:
Packet sent with the DF bit set
MAGNETTE
Success rate is 0% (0/5)

Can I know why is so? and how will this affect my system if MTU failed to 1400?

My tunnel mtu is set to 1400

SH crypto ipsec his:

Path mtu 1452, ip mtu 1452, ip mtu BID Dialer0

Thank you

It is more or less correct...

You don't want to change the IP MTU on a default interface, what you would like to change is the TCP MSS of 1322 inside the router's interface/LAN interface. He will negotiate a lower during the negotiation of the TCP MSS value, when the TCP packet is encrypted by the GRE/ESP or ESP packet, and therefore going through the interface MTU (usually 1 500 bytes) very well.

DMVPN and active directory (logon)

Hi all

We have a DMVPN configuration between a few sites and everything seems fine, except that the logons through the VPN for a new domain active directory are very slow (10-15 minutes). I believe that the problem may be with the fragmentation of tunnel and packages such as AD is configured correctly.

I am looking for some recommendations or advice on the MTU and TCP MSS settings see if it solves the problem.

both the hub and the spokes are currently with the following settings MTU and MSS (ive removed some irrelevant information) Tunnel0 was originally a mtu of 1440 but if whatever it is 1400 is even worse.

Thank you

interface Tunnel0

IP 1400 MTU

IP nat inside

authentication of the PNDH IP SP1

dynamic multicast of IP PNDH map

PNDH network IP-1 id

IP virtual-reassembly in

No cutting of the ip horizon

source of Dialer0 tunnel

multipoint gre tunnel mode

0 button on tunnel

Profile of ipsec protection tunnel 1

interface Dialer0

MTU 1492

the negotiated IP address

NAT outside IP

IP virtual-reassembly in

encapsulation ppp

IP tcp adjust-mss 1452

Dialer pool 1

Dialer-Group 1

Darren,

In general the prolem is due to Kerberos on UDP traffic.

There are several ways you can solve the problem:

(1) transition to Kerberos over TCP. (suggested)

(2) setting the MSS on the interface of tunnel not on telephone transmitter (recommended)

(3) allowing the PMTUD tunnel (strongly recommended).

M.

DMVPN tunnel on a shelf (ADSL Internet access provider)

Hello world

I wonder if I can potentially use same value of pi and the same mtu size of ip tcp mss on the Tunnel interface and interface Fastethernet WAN on my DMVPN spoke routers? WAN interface is facing an ADSL modem provided by the ISP.

That is something like:

Interface FastEthernet 4

IP 1400 MTU

IP tcp adjust-mss 1360

....

Interface Tunnel0

IP 1400 MTU

IP tcp adjust-mss 1360

Will be this questions with fragmentation for DMVPN?

Thank you!

Yes the major impact is the fragmentation and so performance.

I think what you describe is OK and as mentioned turning tunnel PMTUD will take care of some scenarios.

Think of it like this (this is a simplification, but I think as a fitting one).

A 1400 bytes packat happens LAN, we perform the route search, he points through the tunnel interface. We carry out the audit, ' do we need to fragment this packet? The answer is 'no', because it is part of the MTU.

We perform encapsulation (torn by the characteristics applied on the tunnel interface), adding the GRE + IPsec (header GRE, IPsec header and padding).

Now, we take this encapsulated package and check routing post encapuslation, he'll call back via interface fa4.

Don't the packets in the MTU of 1400 feet. 'No', we must fragmed if it is allowed.

VPN online, but some applications like RDP do not work

We currently have a double configuration Dual DMVPN Hub as described in this document http://www.cisco.com/en/US/tech/tk583/tk372/technologies_white_paper09186a008018983e.shtml#dualhubdual

The tunnels are online and allow such as ping and telnet traffic. However other traffic rdp and vnc will not work.

Change the mtu on the tunnel interfaces and using the custom still 'ip of tcp - mss adjust"allow RDP and others.

How do fix us this?

Thank you in advance.

Thanks for posting the configs. I took a look at them and they clarify a number of things.

If applications such as telnet and ping function, then we can be comfortable that it isn't a problem with IPSec. When some applications work and some do not I see several possible explanations:

-There may be an access list that restricts certain traffic. You are saying that the access list is not the problem and since it is not sent I have no way to check that if I accept that is not the issue.

-I see you do things with ip inspect. I didn't understand if there is an intervention of the it. You can evaluate this as a potential problem.

-MTU issues can cause this. I see that you use to set a value of 1440 tcp adjust-mss ip. In my experience of use of ACCORD with IPSec, I found that 1440 was too large. At least as a test, I suggest you set the mss 1375 and see what happens. My reading of the documentation for adjust-mss also indicated that it should be applied to the physical interface where traffic increased. I see that you applied on the tunnel. At least as a test, I suggest that you apply it to physical interfaces, where traffic will pass.

Try these things and let us know if anything changes.

HTH

Rick

Re: Is there a CLI on an AP command to show what controller it is attached?

Hello

I don't see the rcb of the order part. Other thoughts?

Thank you

Tim

1140 #debug lwapp customer?

debugs CC Call Control associated with

LWAPP Client Config Messages config

Customer LWAPP Error Messages error

event Client LWAPP debug event

LWAPP customer Metrics FMC FMC-metrics

your dot11 LWAPP Client redirection

Mgmt dot11 LWAPP customer mgmt

Debug LWAPP Client package package

LWAPP customer Fragment Reassembly reassembly

voice-metrics LWAPP customer voice Metrics

1140 #debug cap

1140 #debug capwap cl

1140 #debug capwap customer?

CAPWAP Client Config Messages config

detail CAPWAP customer detail Messages

Customer CAPWAP Error Messages error

CAPWAP Client Event Messages event

your dot11 CAPWAP Client redirection

hexdump CAPWAP customer Hexdump Messages

Info CAPWAP customer info Messages

LSC LSC events customer CAPWAP

Mgmt Mgmt CAPWAP customer dot11

package, the customer CAPWAP packages

payload CAPWAP customer payload Messages

CAPWAP customer dot11 probe

CAPWAP customer Fragment Reassembly reassembly

customer CAPWAP TCP - mss - MSS adjust adjust

TCP-mss-impression of CAPWAP SMS Client

Tim,

Show {capwap | lwapp} client config, or see the {capwap | lwapp} customer rcb, which will show you "MWAR" you are connected to, and which he knows

See you soon,.
Steve

--

If this helps you or answers to your question if it you please mark it as 'responded' or write it down, if other users can easily find it.

MTU!

Hello

I installed VPN(HUB-spoke) and the VPN connection is OK. Ping is also OK. But when I access the websites of H.O via VPN, the page does not appear.

That's the problem with the MTU size?

My router is a Cisco ISR 2821 with IOS 12.3 (11) T3. This router acts as the firewall and VPN devices.

Does router cisco automatically changes the MTU size for VPN tunnel, when the wan interface is used for the VPN and internet access with the NAT/PAT settings?

-Aline

Vpn IPSec traffic adds about 70 bytes for headers in tunnel mode (20 for the new ip header, 24 for the header ah / esp and around 10-20 more if GRE is used). IPSec VPNs also encapsulate and then fragment, so if you block the fragmented traffic to the HO and then we saw the issue of not getting the trafifc.

With 12.3 IOS T, I believe that there is a command to use a tcp mss/mtu of adjustment, or a substitution of DF (to unplugged the DF bit to allow the fragmentation of the image) on the crypto card and/or the outgoing interface for the router to make the adjustment.

Search Path MTU can not take place if only icmp traffic you allow echo and echo-reply. If you allow inaccessible messages that pmtu can work and you should be able to view the pages. However, that open security holes in order to substitute the mtu/df is the best way to proceed.

Run this test to see if the mtu is causing this issue: on a workstation, set its mtu equal to or less than 1400 max and see if you can view the pages.

If mtu is the case, one or two of these links can help you to understand and resolve the issue.

http://www.Cisco.com/en/us/products/SW/iosswrel/ps1839/products_feature_guide09186a00804247fc.html#wp1052526

http://www.Cisco.com/en/us/customer/products/SW/iosswrel/ps1839/products_feature_guide09186a0080115533.html

Let me know if you need more information.

VPN IPSec L2L between IOS and PIX 6.3 - MTU issue?

The side of the remote control (customer) is behind the 6.3 (5) PIX. And the side of the head end (server) is 2911 IOS on 15.0.

The IPSec tunnel rises very well and passes traffic. However, there is a server which are not fully accessible. Note, it is mainly the web traffic.

Client initiates a connection to the http://server:8000. They receive a redirect to go to http://server:8000 / somepage.jspa. Package caps show the customer acknowledges the redirect with a SYN - ACK response, but then the connection just hangs. And no other packets are received in return. I noticed that the redirected page is a .jsp and other pages that work OK are not. I also noticed that some MTU and TCP MSS configurations on the side of the head that are in place for another GRE VPN tunnel with another site. So I got in the way of the fragmentation of packets. The side PIX has all the standard configurations of IPSec as well as default MTU on the interface of the inside and outside.

When the MTU is set manually on the client computer to 1400, the access to the works of http://server:8000 / somepage.jspa very well. So I need to tweak the settings of PIX. I tried to adjust the MTU size on and abroad the interface as well as the parameter "sysopt connection tcp - mss. I don't know what else to do here.

Here is a summary of the MTU settings on the head of line:

End of the head:

int tunnel0 (it's the GRE tunnel)

IP mtu 1420

source of tunnel G0/0

dest X.X.X.X

tunnel path-mtu-discovery

card crypto vpn 1

tunnel GRE Description

blah blah blah

card crypto vpn 2

Description IPSec tunnel

blah blah blah

int g0/0 (external interface)

no ip redirection

no ip unreachable

no ip proxy-arp

Check IP unicast reverse

NAT outside IP

IP virtual-reassembly

vpn crypto card

int g0/1 (this is the interface to the server in question)

no ip redirection

no ip unreachable

no ip proxy-arp

IP nat inside

IP virtual-reassembly

IP tcp adjust-mss 1452

HA, sorry my bad. Read the previous post wrong.

(Note: Yes, the SMS on the tunnel interface should be 40 bytes less than MTU).

Do not twist the MTU, not for TCP problems (not as the first step), it is safer to play with the MSS. MTU may depend on other things (OSPF for example).

Make a sweep of a ping with DF bit set with the size (from 1300 bytes for example). By doing this, you want to check what is the maximum size of the package, which you can test through the IPsec tunnel. Once you have this value consider - subtract 40 and this defined as value MSS of the LAN interface (and adjust the value of PIX if you can).

M.

Default gateway when connected to the VPN

Thanks for reading!

It is probably a dump so bear with me the question...

I set up a VPN connection with a Cisco ASA 5505 giving over the internet, with customers behind him (on the same subnet), when environmental connected ot the VPN I can reach the router inside giving me and the other pass behind the router (each switch is connected to the router), but nothing else.

My beets is that the router is to play with my connection, but nevermind that!, Setup is not complete when even... my question is more related to the bridge I'm missing when I'm outside, is connected to VPN on the ASA, pourrait this BUMBLE? I would not a Standard gateway in the command ipconfig settings in windows?

That's who it looks like now:

Anslutningsspecifika-DNS suffix. : VPNOFFICE

IP-adress...: 10.10.10.1

Natmask...: 255.255.255.0.

Standard-gateway...:

The internal network is:

172.16.12.0 255.255.255.0

Here is my config for the SAA, thank you very much!

! FlASH PA ROUTING FRAN VISSTE

! asa841 - k8.bin

!

DRAKENSBERG hostname

domain default.domain.invalid

activate the password XXXXXXX

names of

!

interface Vlan1

nameif inside

security-level 100

IP 172.16.12.4 255.255.255.0

!

interface Vlan10

nameif outside

security-level 0

IP 97.XX. XX.20 255.255.255.248

!

interface Ethernet0/0

switchport access vlan 10

!

interface Ethernet0/1

!

interface Ethernet0/2

!

interface Ethernet0/3

!

interface Ethernet0/4

!

interface Ethernet0/5

!

interface Ethernet0/6

!

interface Ethernet0/7

!

passive FTP mode

clock timezone THATS 1

clock to summer time CEDT recurring last Sun Mar 02:00 last Sun Oct 03:00

DNS server-group DefaultDNS

domain default.domain.invalid

object-group Protocol TCPUDP

object-protocol udp

object-tcp protocol

172.16.12.0 IP Access-list extended sheep 255.255.255.0 allow 10.10.10.0 255.255.255.0

MSS_EXCEEDED_ACL list extended access permitted tcp a whole

Note to access VPN-SPLIT-TUNNEL VPN TUNNEL from SPLIT list

standard of TUNNEL VPN-SPLIT-access list permits 172.16.12.0 255.255.255.0

!

map-TCP MSS - map

allow to exceed-mss

!

pager lines 24

Enable logging

timestamp of the record

exploitation forest-size of the buffer to 8192

notifications of recording console

logging buffered stored notifications

notifications of logging asdm

Within 1500 MTU

Outside 1500 MTU

mask pool local 10.10.10.1 - 10.10.10.40 VPN IP 255.255.255.0

ICMP unreachable rate-limit 1 burst-size 1

ICMP allow any inside

ICMP allow all outside

ASDM image disk0: / asdm-625 - 53.bin

don't allow no asdm history

ARP timeout 14400

Global 1 interface (outside)

NAT (inside) 0 access-list sheep

NAT (inside) 1 172.16.12.0 255.255.255.0

Route outside 0.0.0.0 0.0.0.0 97.XX. XX.17 1

Timeout xlate 03:00

Timeout conn 01:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02

Sunrpc timeout 0:10:00 h323 0:05:00 h225 mgcp from 01:00 0:05:00 mgcp-pat 0:05:00

Sip timeout 0:30:00 sip_media 0:02:00 prompt Protocol sip-0: 03:00 sip - disconnect 0:02:00

Timeout, uauth 0:05:00 absolute

dynamic-access-policy-registration DfltAccessPolicy

the ssh LOCAL console AAA authentication

Enable http server

http 172.16.12.0 255.255.255.0 inside

No snmp server location

No snmp Server contact

Server enable SNMP traps snmp authentication linkup, linkdown cold start

Crypto ipsec transform-set ESP-AES-256-MD5 esp-aes-256 esp-md5-hmac

Crypto ipsec transform-set ESP-DES-SHA esp - esp-sha-hmac

Crypto ipsec transform-set ESP-DES-MD5 esp - esp-md5-hmac

Crypto ipsec transform-set ESP-AES-192-MD5 esp-aes-192 esp-md5-hmac

Crypto ipsec transform-set ESP-3DES-MD5-esp-3des esp-md5-hmac

Crypto ipsec transform-set ESP-AES-256-SHA 256 - aes - esp esp-sha-hmac

Crypto ipsec transform-set ESP-AES-128-SHA aes - esp esp-sha-hmac

Crypto ipsec transform-set ESP-AES-192-SHA esp-aes-192 esp-sha-hmac

Crypto ipsec transform-set ESP-AES-128-MD5-esp - aes esp-md5-hmac

Crypto ipsec transform-set esp-SHA-ESP-3DES-3des esp-sha-hmac

crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 pfs Group1 set

Crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 value transform-set ESP-AES-128-SHA ESP-AES-128-MD5 ESP-AES-192-SHA ESP-AES-192-MD5 ESP-AES-256-SHA ESP-AES-256-MD5 ESP-3DES-SHA MD5-ESP-3DES ESP-DES-SHA ESP-DES-MD5

outside_map card crypto 65535-isakmp dynamic ipsec SYSTEM_DEFAULT_CRYPTO_MAP

outside_map interface card crypto outside

crypto ISAKMP allow outside

crypto ISAKMP policy 10

preshared authentication

3des encryption

sha hash

Group 2

life 86400

crypto ISAKMP policy 65535

preshared authentication

3des encryption

sha hash

Group 2

life 86400

Telnet timeout 5

SSH 172.16.12.0 255.255.255.0 inside

SSH timeout 5

Console timeout 0

!

a basic threat threat detection

Statistics-list of access threat detection

internal VPNOFFICE group policy

VPNOFFICE group policy attributes

value of server DNS 215.122.145.18

Protocol-tunnel-VPN IPSec

Split-tunnel-policy tunnelspecified

Split-tunnel-network-list value TUNNEL VPN-SPLIT

value by default-field VPNOFFICE

Split-dns value 215.122.145.18

no method of MSIE-proxy-proxy

username password admin privilege 15 XXXXXX

username privilege XXXXX Daniel password 0

username Daniel attributes

VPN-group-policy VPNOFFICE

type tunnel-group VPNOFFICE remote access

attributes global-tunnel-group VPNOFFICE

VPN address pool

Group Policy - by default-VPNOFFICE

IPSec-attributes tunnel-group VPNOFFICE

pre-shared key XXXXXXXXXX

!

class-map MSS_EXCEEDED_MAP

corresponds to the MSS_EXCEEDED_ACL access list

class-map inspection_default

match default-inspection-traffic

!

!

type of policy-card inspect dns preset_dns_map

parameters

message-length maximum 512

Policy-map global_policy

class inspection_default

inspect the preset_dns_map dns

inspect the ftp

inspect h323 h225

inspect the h323 ras

inspect the netbios

inspect the rsh

inspect the rtsp

inspect the skinny

inspect esmtp

inspect sqlnet

inspect sunrpc

inspect the tftp

inspect the sip

inspect xdmcp

inspect the icmp error

inspect the pptp

inspect the amp-ipsec

inspect the icmp

class MSS_EXCEEDED_MAP

advanced connection options MSS-map

!

global service-policy global_policy

privilege level 3 mode exec cmd command perfmon

privilege level 3 mode exec cmd ping command

mode privileged exec command cmd level 3

logging of the privilege level 3 mode exec cmd commands

privilege level 3 exec command failover mode cmd

privilege level 3 mode exec command packet cmd - draw

privilege show import at the level 5 exec mode command

privilege level 5 see fashion exec running-config command

order of privilege show level 3 exec mode reload

privilege level 3 exec mode control fashion show

privilege see the level 3 exec firewall command mode

privilege see the level 3 exec mode command ASP.

processor mode privileged exec command to see the level 3

privilege command shell see the level 3 exec mode

privilege show level 3 exec command clock mode

privilege exec mode level 3 dns-hosts command show

privilege see the level 3 exec command access-list mode

logging of orders privilege see the level 3 exec mode

privilege, level 3 see the exec command mode vlan

privilege show level 3 exec command ip mode

privilege, level 3 see fashion exec command ipv6

privilege, level 3 see the exec command failover mode

privilege, level 3 see fashion exec command asdm

exec mode privilege see the level 3 command arp

command routing privilege see the level 3 exec mode

privilege, level 3 see fashion exec command ospf

privilege, level 3 see the exec command in aaa-server mode

AAA mode privileged exec command to see the level 3

privilege, level 3 see fashion exec command eigrp

privilege see the level 3 exec mode command crypto

privilege, level 3 see fashion exec command vpn-sessiondb

privilege level 3 exec mode command ssh show

privilege, level 3 see fashion exec command dhcpd

privilege, level 3 see the vpnclient command exec mode

privilege, level 3 see fashion exec command vpn

privilege level see the 3 blocks from exec mode command

privilege, level 3 see fashion exec command wccp

privilege, level 3 see the exec command in webvpn mode

privilege control module see the level 3 exec mode

privilege, level 3 see fashion exec command uauth

privilege see the level 3 exec command compression mode

level 3 for the show privilege mode configure the command interface

level 3 for the show privilege mode set clock command

level 3 for the show privilege mode configure the access-list command

level 3 for the show privilege mode set up the registration of the order

level 3 for the show privilege mode configure ip command

level 3 for the show privilege mode configure command failover

level 5 mode see the privilege set up command asdm

level 3 for the show privilege mode configure arp command

level 3 for the show privilege mode configure the command routing

level 3 for the show privilege mode configure aaa-order server

level mode 3 privilege see the command configure aaa

level 3 for the show privilege mode configure command crypto

level 3 for the show privilege mode configure ssh command

level 3 for the show privilege mode configure command dhcpd

level 5 mode see the privilege set privilege to command

privilege level clear 3 mode exec command dns host

logging of the privilege clear level 3 exec mode commands

clear level 3 arp command mode privileged exec

AAA-server of privilege clear level 3 exec mode command

privilege clear level 3 exec mode command crypto

level 3 for the privilege cmd mode configure command failover

clear level 3 privilege mode set the logging of command

privilege mode clear level 3 Configure arp command

clear level 3 privilege mode configure command crypto

clear level 3 privilege mode configure aaa-order server

context of prompt hostname

Cryptochecksum:aaa1f198bf3fbf223719e7920273dc2e

: end

Right if disbaled all traffic will pass tunnel and snack active local internet gateway is used specific traffic wil go to the tunnel.

IP tcp adjust-mss does not

Hello

I setup ip tcp adjust-mss at 1200 on a router interface and when you make a packet trace I still see value MSS appearing as 1460 in the initial SYN packet.

The configuration is the following; I have a pc connected to a router on Fa0/0. I placed the order 'adjust a segment tcp ip - mss 1200' in the configuration of the Fa0/0 interface. This router then connects to another router. I have a telnet from the host pc for the remote router, then the SYN passes through the router I lowered the MSS value on and it is not just changing. I am using wireshark to check. Am I missing something or is this supposed to tell the router to intercept packets SYN and change the MSS value?

Any help is very appreciated.

Sincerely,

David

Hi Dave,.

The SYN-ACK with MSS as 536 is planned. Most platforms use 536 default MSS. During the TCP 3 way handshaking, any side has small size that MSS will be used.

HTH,

Lei Tian

TCP Window Scaling issues

We have Cisco 2800 to each of our four locations that are managed by our ISP. We had problems with them, I got them to send me the configuration files of one of them, but nothing jumps out to me.

You must disable TCP Window Scaling/tuning on all our Machines 7/Server Windows 2012 (by running netsh interface tcp set global autotuning = disabled in the command line)

If we have not this is very slow to load even a Web page and cannot download a file (even something as small as 2 MB). Mobile devices have no hope to work on our network now because of this. This isn't a question on our XP remaning machines bit, but I think that XP did not use Window Scaling is the reason.

Any ideas what could be causing this? I intend to replace it soon with our own routers, because they do not want to configure the secondary interfaces for our VLAN, but in the meantime I need this job.

Thanks in advanced for any help.

Here is the Config with Sensative information deleted

version 12.3

no service pad

service tcp-keepalives-in

service tcp-keepalives-out

service timestamps debug datetime msec localtime show-timezone

service timestamps log datetime msec localtime show-timezone

service password-encryption

service sequence-numbers

hostname REMOVED

boot-start-marker

boot-end-marker

logging buffered 8192 debugging

no logging console

enable secret REMOVED

no aaa new-model

resource policy

mmi polling-interval 60

no mmi auto-configure

no mmi pvc

mmi snmp-timeout 180

ip subnet-zero

ip cef

no ip dhcp use vrf connected

ip inspect name DEFAULT100 cuseeme

ip inspect name DEFAULT100 ftp

ip inspect name DEFAULT100 h323

ip inspect name DEFAULT100 icmp

ip inspect name DEFAULT100 netshow

ip inspect name DEFAULT100 rcmd

ip inspect name DEFAULT100 realaudio

ip inspect name DEFAULT100 rtsp

ip inspect name DEFAULT100 esmtp

ip inspect name DEFAULT100 sqlnet

ip inspect name DEFAULT100 streamworks

ip inspect name DEFAULT100 tftp

ip inspect name DEFAULT100 tcp

ip inspect name DEFAULT100 udp

ip inspect name DEFAULT100 vdolive

no ip ips deny-action ips-interface

no ftp-server write-enable

crypto pki trustpoint TP-self-signed-REMOVED

enrollment selfsigned

subject-name cn=IOS-Self-Signed-Certificate-REMOVED

revocation-check none

rsakeypair TP-self-signed-REMOVED

crypto pki certificate chain TP-self-signed-REMOVED

certificate self-signed 01

REMOVED

quit

class-map match-all VOIP

match access-group 120

policy-map VOIP

class VOIP

priority 1000

class class-default

crypto isakmp policy 1

encr 3des

authentication pre-share

group 2

crypto isakmp key REMOVED address 0.0.0.0 0.0.0.0

no crypto isakmp ccm

crypto ipsec transform-set VPN esp-aes 256 esp-sha-hmac

crypto ipsec profile SDM_Profile1

set transform-set VPN

crypto ipsec profile SDM_Profile2

set transform-set VPN

interface Tunnel0

description $FW_INSIDE$

bandwidth 3000

ip address 10.10.200.1 255.255.255.0

ip access-group 101 in

no ip redirects

ip mtu 1400

ip nhrp authentication VPN

ip nhrp map multicast dynamic

ip nhrp network-id 100000

ip nhrp holdtime 360

ip virtual-reassembly

ip route-cache flow

ip tcp adjust-mss 1360

ip ospf network broadcast

ip ospf priority 20

delay 10

tunnel source FastEthernet0/1

tunnel mode gre multipoint

tunnel key 100000

tunnel protection ipsec profile SDM_Profile1

interface Null0

no ip unreachables

interface Loopback0

ip address 192.168.210.1 255.255.255.255

no ip redirects

no ip unreachables

no ip proxy-arp

ip route-cache flow

interface FastEthernet0/0

description $FW_INSIDE$

ip address 10.10.100.1 255.255.255.0

ip access-group 100 in

no ip redirects

no ip unreachables

no ip proxy-arp

ip nat inside

ip virtual-reassembly

ip route-cache flow

ip policy route-map server-nat

duplex auto

speed auto

no mop enabled

service-policy output VOIP

interface FastEthernet0/1

description $FW_OUTSIDE$

ip address IP REMOVED NETMASK REMOVED

ip access-group 102 in

ip verify unicast reverse-path

no ip redirects

no ip unreachables

no ip proxy-arp

ip nat outside

ip inspect DEFAULT100 out

ip virtual-reassembly

ip route-cache flow

load-interval 30

duplex auto

speed auto

no mop enabled

interface FastEthernet0/1/0

load-interval 30

interface FastEthernet0/1/1

interface FastEthernet0/1/2

interface FastEthernet0/1/3

router ospf 100

log-adjacency-changes

passive-interface FastEthernet0/0

passive-interface FastEthernet0/1

passive-interface FastEthernet0/1/0

network 10.10.100.0 0.0.0.255 area 0

network 10.10.200.0 0.0.0.255 area 0

network 10.10.201.0 0.0.0.255 area 0

network 192.168.210.1 0.0.0.0 area 0

ip classless

ip route 0.0.0.0 0.0.0.0 REMOVED

ip route REMOVED NETMASK REMOVED

ip flow-capture ip-id

ip flow-capture mac-addresses

ip flow-top-talkers

top 10

sort-by bytes

cache-timeout 30000

ip http server

ip http authentication local

ip http secure-server

ip nat pool nat REMOVED netmask REMOVED

ip nat inside source list 150 interface FastEthernet0/1 overload

access-list 100 deny ip 10.10.200.0 0.0.0.255 any

access-list 100 deny ip host 255.255.255.255 any

access-list 100 deny ip 127.0.0.0 0.255.255.255 any

access-list 100 permit ip any any

access-list 100 deny ip 10.10.201.0 0.0.0.255 any

access-list 101 remark Tunnel ACL

access-list 101 deny ip REMOVED 0.0.0.7 any log

access-list 101 deny ip host 255.255.255.255 any log

access-list 101 deny ip 127.0.0.0 0.255.255.255 any log

access-list 101 permit ip 10.10.100.0 0.0.0.255 10.10.110.0 0.0.0.255 log

access-list 101 permit ip 10.10.100.0 0.0.0.255 10.10.120.0 0.0.0.255 log

access-list 101 permit ip 10.10.100.0 0.0.0.255 10.10.130.0 0.0.0.255 log

access-list 101 permit ip host 10.10.100.10 any log

access-list 101 permit ip host 10.10.100.12 any log

access-list 101 permit ip host 10.10.100.20 any log

access-list 101 permit ip host 10.10.100.21 any log

access-list 101 permit ip host 10.10.100.45 any log

access-list 101 permit ip any host 10.10.100.10 log

access-list 101 permit ip any host 10.10.100.12 log

access-list 101 permit ip any host 10.10.100.20 log

access-list 101 permit ip any host 10.10.100.21 log

access-list 101 permit ip any host 10.10.100.45 log

access-list 101 permit ospf any any

access-list 101 permit icmp any any

access-list 101 deny ip 10.10.100.0 0.0.0.255 any log

access-list 101 permit ip 10.10.110.0 0.0.0.255 10.10.100.0 0.0.0.255

access-list 101 permit ip 10.10.120.0 0.0.0.255 10.10.100.0 0.0.0.255

access-list 101 permit ip 10.10.130.0 0.0.0.255 10.10.100.0 0.0.0.255

access-list 102 remark Outside ACL

access-list 102 permit tcp host REMOVED host REMOVED eq 22

access-list 102 permit tcp REMOVED 0.0.0.15 host REMOVED eq 22

access-list 102 permit udp any host REMOVED eq non500-isakmp

access-list 102 permit udp any host REMOVED eq isakmp

access-list 102 permit esp any host REMOVED

access-list 102 permit ahp any host REMOVED

access-list 102 permit gre any host REMOVED

access-list 102 permit icmp any host REMOVED echo-reply

access-list 102 permit icmp any host REMOVED time-exceeded

access-list 102 permit icmp any host REMOVED unreachable

access-list 102 permit ip any host 10.10.100.10

access-list 102 permit ip any host 10.10.100.12

access-list 102 permit ip any host 10.10.100.20

access-list 102 permit ip any host 10.10.100.21

access-list 102 permit ip any host 10.10.100.45

access-list 102 deny ip 10.10.100.0 0.0.0.255 any

access-list 102 deny ip 10.10.200.0 0.0.0.255 any

access-list 102 deny ip 10.0.0.0 0.255.255.255 any

access-list 102 deny ip 172.16.0.0 0.15.255.255 any

access-list 102 deny ip 192.168.0.0 0.0.255.255 any

access-list 102 deny ip 127.0.0.0 0.255.255.255 any

access-list 102 deny ip host 255.255.255.255 any

access-list 102 deny ip host 0.0.0.0 any

access-list 103 permit ip REMOVED 0.0.0.15 any

access-list 103 permit ip 10.10.200.0 0.0.0.255 any

access-list 103 permit ip 10.10.100.0 0.0.0.255 any

access-list 103 permit ip 10.10.110.0 0.0.0.255 any

access-list 103 permit ip 10.10.120.0 0.0.0.255 any

access-list 103 permit ip 10.10.130.0 0.0.0.255 any

access-list 110 deny ip host 10.10.100.12 10.10.110.0 0.0.0.255

access-list 110 deny ip host 10.10.100.12 10.10.130.0 0.0.0.255

access-list 110 deny ip host 10.10.100.10 10.10.110.0 0.0.0.255

access-list 110 deny ip host 10.10.100.10 10.10.130.0 0.0.0.255

access-list 110 deny ip host 10.10.100.20 10.10.110.0 0.0.0.255

access-list 110 deny ip host 10.10.100.20 10.10.130.0 0.0.0.255

access-list 110 deny ip host 10.10.100.21 10.10.110.0 0.0.0.255

access-list 110 deny ip host 10.10.100.21 10.10.130.0 0.0.0.255

access-list 110 deny ip host 10.10.100.45 10.10.110.0 0.0.0.255

access-list 110 deny ip host 10.10.100.45 10.10.130.0 0.0.0.255

access-list 110 permit ip host 10.10.100.12 any

access-list 110 permit ip host 10.10.100.10 any

access-list 110 permit ip host 10.10.100.20 any

access-list 110 permit ip host 10.10.100.21 any

access-list 110 permit ip host 10.10.100.45 any

access-list 120 permit udp any any eq 5060

access-list 150 deny ip host 10.10.100.10 any

access-list 150 deny ip host 10.10.100.12 any

access-list 150 deny tcp host 10.10.100.20 any eq 3389

access-list 150 deny ip host 10.10.100.21 any

access-list 150 deny tcp host 10.10.100.45 any eq 22

access-list 150 deny tcp host 10.10.100.45 any eq 443

access-list 150 deny udp host 10.10.100.45 any eq 5060

access-list 150 deny udp host 10.10.100.45 any range 10000 10500

access-list 150 deny ip 10.10.110.0 0.0.0.255 any

access-list 150 deny ip 10.10.120.0 0.0.0.255 any

access-list 150 deny ip 10.10.130.0 0.0.0.255 any

access-list 150 permit ip 10.10.100.0 0.0.0.255 any

route-map server-nat permit 10

match ip address 110

set ip next-hop 10.10.200.3

control-plane

banner motd ^CC

<@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@>

Authorized access only

<@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@>

Disconnect IMEDIATELY if you are not an authorized user !

line con 0

transport output telnet

line aux 0

transport output telnet

line vty 0 4

access-class 103 in

privilege level 15

transport input ssh

line vty 5 15

access-class 103 in

privilege level 15

transport input ssh

end

Hello Jason,

you will find articles from may saying that MS AutoFix feature does not work well with some firewall stateful inspection and/or VPN.

At CSC, I found another interesting:

https://supportforums.Cisco.com/thread/2169557

Maybe Joseph joins this discussion later with some new or additional information.

Best regards

Rolf

TCP MSS

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