WAG160n DHCP issues

Similar Questions

• E1200 DHCP issue?

  I want to use my E1200 on my existing network which already has another device with internet access.  Currently, this network doesn't have a DHCP server.  I want to use the DHCP of the E1200 to give my customers IP addressing, but I want to assign the default gateway of the Internet, not the E1200 connected device.  I don't want to change my current network IP addressing.  Is this possible? I'm not having a bit of luck to find a way to give an address via DHCP default gateway for one IP address other than the IP address of the E1200 itself?  Thank you!

  Unfortuantely you can't because it's DHCP will automatically set the IP address of the gateway to himself.

• VLAN voice N3048P and DHCP issues

  Hello

  I just received several switches for our N3048P and 2 x 4048 access layer - WE for our base layer. Are the N3048P VLT'd between two of 4048. There are 4 x N3048P of one on the other. The 4048 possess all gateways via VRRP.

  I have 802. 1 x works with my Windows client test, and I can get the phone (Cisco 7941) to acquire a DHCP address if I put it on a port "switchport mode access. However, if I change the port to a general port with vlan enabled voice and 802. 1 x, the phone does not have a DHCP address, but the PC attached to the phone Gets a DHCP address in the VLAN correct.

  I see CDP and LLDP messages exchanged via Wireshark, and it seems that the phone and the switch are to exchange the VLAN voice correctly.

  My question is, why the phone can't one address DHCP?

  Here's the relevant config of switch below. I know that some of the config can be duplicated for troubleshooting steps:

  VLAN 75
  the name 'Test '.
  output
  VLAN 76
  name "Test_Phones".
  output

  IP helper-address 1.1.1.3 dhcp
  IP helper-address 1.1.1.4 dhcp

  interface vlan 75
  IP 172.16.75.4 255.255.255.0
  IP helper 1.1.1.3
  IP helper 1.1.1.4
  output
  interface vlan 76
  IP 172.16.76.4 255.255.255.0
  IP helper 1.1.1.3
  IP helper 1.1.1.4

  AAA authentication local connection to "defaultList".
  radius of start-stop AAA accounting dot1x default
  control-dot1x system-auth
  radius AAA dot1x default authentication service
  AAA authorization network default RADIUS

  VLAN, VoIP

  source-ip 172.16.75.4 RADIUS server
  Server RADIUS 'key' key
  RADIUS-server host 1.1.1.1 auth
  primary
  name "rad1.
  use of 802. 1 x
  key 'key '.
  output
  RADIUS-server host 1.1.1.2 auth
  name "rad2.
  use of 802. 1 x
  key 'key '.
  output
  Server RADIUS acct 1.1.1.1 host
  name "rad1.
  output
  host server RADIUS acct 1.1.1.2
  name "rad2.
  output

  Gi2/0/1 interface

  Description '802. 1 x client port.
  spanning tree portfast
  spanning tree guard root
  switchport mode general
  switchport general allowed vlan add 75-76 the tag
  dot1x re-authentication
  dot1x quiet-period 5
  dot1x tx-period 5
  dot1x comments - vlan 20
  dot1x Informati-vlan 20
  LLDP transmit tlv ESCR-sys sys - cap
  LLDP transmit-mgmt
  notification of LLDP
  LLDP-med confignotification
  VLAN voice 76
  disable voice vlan auth
  output

  Thanks for any input you may have. I would like to know if there is any other information, I can provide.

  -Jason

  That ends up being the correct port configuration:

  Gi2/0/1 interface

  Description '802. 1 x client port.

  spanning tree portfast

  switchport mode general

  switchport General pvid 75

  VLAN allowed switchport General add 75

  switchport general allowed vlan add 76 tag

  dot1x port-control on mac

  dot1x re-authentication

  dot1x quiet-period 5

  dot1x timeout supp-timeout 15

  dot1x tx-period 5

  dot1x comments-vlan-deadline 15

  dot1x comments - vlan 20

  dot1x Informati-vlan 20

  VLAN voice 76

  disable voice vlan auth

  The most important line here is «the dot1x port-control on mac» I got 'auto control by port dot1x' configured, but it does not work as expected. In addition, defining the comments-vlan-period and supp-timeout were necessary. If the port was shot, the switch would not necessarily reauth port.

• client DHCP issues with 4400 WLC

  The ACS authentication works very well.

  Clients cannot obtain an IP address from the DHCP server.

  DHCP server is configured on a dynamic interface but is on a different subnet located in a branch office. The DHCP scope is running on a switch 4500 in the branch.

  It is preferable to have DHCP works on internal WLC or near the WLC, rather than DHCP server at the remote location?

  TIA

  Generally, you don't want to have a dhcp server on a remote site, but it should also work as wired users are able to get an IP address from the remote dhcp server. Preferred, as I have said, is to have a local dhcp server, but if this does not work for you, then by configuring the wlc to bbe a dhcp server is not a bad thought either. Some, like to have more control over the dhcp.

• RV110W DHCP issue?

  Rv110w, I have 4 VLANS.

  vlan3 feeds a mute switch and a wireless access point. Looking at the router DHCP leases, it shows connected and non-connected devices. A little as it does not refresh the list. The 50 value leases. Questions: Is this normal? How often to refresh? -What time DHCP set like minutes?

  Thanks a lot for the provision of related information.

  Well, if you have 50 IP pool and 50 users connect and disconnect in the day, I would expect that you can escape. I put the DHCP lease for 1 to 2 hours, so you can keep a constant "Refresh" of this and this problem should disappear.

  -Tom
  Please mark replied messages useful

• AP DHCP issues after that 4500 IOS upgraded

  Hello

  Since we went to-: cat4500e-entservicesk9 - mz.122 - 54.SG.bin on our 4500 we had problems with our AP CAPWAP onto our 5500 controller.

  Debugs showed AP, that he cannot receive the IP address.

  DHCP: SDiscover 302 bytes
  * 00:37:02.140 Mar 1: B'cast on the interface GigabitEthernet0 0.0.0.0
  * 00:37:03.999 Mar 1: % CAPWAP-3-Journal of ERRORS: do not send discovery request AP doesn't have an Ip address.
  * 00:37:06.141 Mar 1: DHCP: attempt to SDiscover # 3 for entry:
  * 00:37:06.141 Mar 1: Temp IP addr: 0.0.0.0 for peer on Interface: GigabitEthernet0
  * 00:37:06.141 Mar 1: Temp subnet mask: 0.0.0.0
  * 00:37:06.141 Mar 1: DHCP Lease server: 0.0.0.0, State: 1 selection
  * 00:37:06.141 Mar 1: DHCP transaction id: BF5
  * 00:37:06.141 Mar 1: lease: 0 seconds, renewal: 0 seconds, relink: 0 seconds
  * 00:37:06.141 Mar 1: next timer triggers after: 00:00:04
  * 00:37:06.141 Mar 1: number of attempts: 3 Client-ID: f866.f21d.39d4
  * 00:37:06.141 Mar 1: hexadecimal dumping ID Client: F866F21D39D4
  * 00:37:06.141 Mar 1: host name: APf866.f21d.39d4
  * 00:37:06.141 Mar 1: DHCP: set SDiscover option class-id: 436973636F204150206333353030
  * 00:37:06.141 Mar 1: DHCP: SDiscover: sending of DHCP package for the length 302 bytes
  * 00:37:06.141 Mar 1: DHCP: 302 SDiscover bytes
  * 00:37:06.141 Mar 1: B'cast on the interface GigabitEthernet0 0.0.0.0
  * 00:37:10.143 Mar 1: DHCP: QScan: Timed out selecting State
  * 00:37:13.999 Mar 1: % CAPWAP-3-Journal of ERRORS: do not send discovery request AP doesn't have an Ip address. DHCP problem % unknown... No possible allocation
  * 00:37:19.265 Mar 1: DHCP: waiting for 10 seconds on the interface GigabitEthernet0
  Not in a bound State.

  I did debug on the controller, it gives the address over and over again. I don't see any message CAPWAP and the AP do not have an IP address.

  Not sure if I should roll back IOS, I see not an IOS cause such a problem?

  Any information would be appreciated...

  Thank you

  Brad

  Can do without the configuration of the DHCP server to any device L3 just in order to test?

  http://Tools.Cisco.com/support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCth68708

  Bugs are always trigger... they don't knock code time that execute us...

  It will be great if we could apply externally and do a test...

  Let me know if that answers your question...

  Concerning
  Surendra
  ====
  Please do not forget to note positions that answered your question and mark as answer or was useful

• Proxy DHCP issue

  I use the 'Network DHCP scope' field in order to give a specific scope for a group of users. The VPN concentrator for the DHCP Discover request uses its own IP address in the source IP field and inserts into the GIADDR in the DHCP Discover message information "network DHCP scope. The DHCP server then uses the GIADDR as the return address, and therefore my VPN concentrator does not receive the DHCP Offer.

  Does anyone have a solution or information?

  Thank you.

  Kind regards.

  David Roy.

  You must configure the routing of your internal network so that any subnet you defined is routed to the private hub interface.

  For example, suppose you put 200.1.1.1 field of the DHCP network scope according to group settings. This IP address can be in the GIADDR field in the DHCP request sends the hub. The DHCP server response will be unicast to 200.1.1.1, with an IP address in the 200.1.1.0 subnet assigned within the DHCP package. Your internal network must deliver this network to the private IP hub, not only for the answer DHCP to make it again, but for the following to all packages of VPN clients to make return as.

  You cannot allocate a DHCP scope of network for a subnet existing on your network, because when the VPN clients send packets, the answers to these will be sent out of this existing subnet. Responses to VPN clients, including the response to the original request to DHCP from the hub must be routed to the hub itself.

• DHCP issues

  I installed VMware Workstation 10 on my laptop (Win8) and built the following virtual machines:

  1 Windows Server 2008 (AD, DNS and DHCP)

  2 Windows 7

  the network settings of the VM workstation, I put the NIC as 'host-only' because I want only the communication between the server and 2 win7 clients.

  My problem is that the 2 Win7 clients get IPs from my laptop and not DHCP server. Setting up a static IP on the Win7 clients seems to work.

  How can I solve this problem of DHCP IP setting manually on clients in Win7? Help, please.

  Use the button "add a network...". "in the virtual network Editor, and then select the option you want or need.

  André

• Network/DNS/DHCP issues with testlab - virtual network Editor is killing me!

  Hey all - a little new with workstation and have been messing around trying to get this to work for so long, I want to just set up my lab already but can't find the catch here.

  So, here is what I tried to do:

  Have a hand of Windows Server 2008 R2 (Controller/DHCP/DNS/Active Directory domain / IIS) addresses/leases DHCP of an internal network (which means, I want some Windows 7 Ultimate customers to assign IPs to the DC and NOT of VMWare offers integrated DHCP). I want clients to be able to use only one NIC (preferably) and both authenticate to AD and connect to the Internet (so I think I'll pass on DNS to resolve external domains?). I'm having a pretty hard time trying to understand what...

  My physical network is an active router Linksys with DHCP, so them to assign an IP address to the PC that I'm looking for this laboratory-perhaps it is a problem as well and must also be configured or have my VMNet reflecting?

  I tried to use NAT, a bridge connection, etc... and even then, when I got my DC with an active internet connection, how would I configure my clients (Win7 devices) to join the network even on my domain controller is? I tried some configurations in these forums as well, but none seems to for what I'm trying (which seems very simple!). Can anyone offer some advice? I am not opposed to the fresh start. Thanks for taking a peek.

  Here is an example of configuration when all the virtual machines are configured for NAT.

  Virtual network Editor:

  DHCP disabled for NAT

  For an example, I assume that the NAT subnet in 192.168. 100. x. You can change this if you wish.

  DC:

  IP address: 192.168.100.10

  Subnet mask: 255.255.255.0

  Gateway: 192.168.100.2

  DNS server: 127.0.0.1

  Configuration of the DHCP server:

  Range: 192.168.100.150... 200

  Subnet: 255.255.255.0

  Gateway: 192.168.100.2

  DNS server: 192.168.100.10

  The DNS server configuration:

  DNS forwarding to: 192.168.100.2 (for other than the own domain URLS)

  Other servers or systems with static IP settings:

  IP address: 192.168.100.11... 149

  Subnet mask: 255.255.255.0

  Gateway: 192.168.100.2

  DNS server: 192.168.100.10

  Customer:

  Networking will be set to automatic.

  In this way, the domain controller will be the only DHCP and DNS server, but each virtual computer will be able to access directly to the Internet. And because the domain controller is the primary DNS, your ad cannot function properly.

  André

• Cisco 877W DHCP does not automatically fill the Windows/Mac customers with DNS server entries

  I have a 877W which was operational on Verizon for about 5 years. It never automatically distributed info DNS server for customers who get DHCP issued IP address. I have to manually enter the DNS entries to each client.  What happened to other sites where I've got installed on AT & T as well as 877 unified communications.

  Here is the config. Thanks in advance for the help.

  Building configuration...

  Current configuration: 7987 bytes
  !
  version 12.4
  no service button
  tcp KeepAlive-component snap-in service
  a tcp-KeepAlive-quick service
  horodateurs service debug datetime localtime show-timezone msec
  Log service timestamps datetime localtime show-timezone msec
  encryption password service
  sequence numbers service
  !
  Cod of hostname
  !
  boot-start-marker
  boot-end-marker
  !
  logging buffered debugging 51200
  recording console critical
  enable secret 5 jSwA $1$ $ 3B5lJNqm0ewh
  !
  AAA new-model
  !
  !
  AAA authentication local-to-remote login
  local remote of the AAA authorization network
  !
  AAA - the id of the joint session
  !
  resources policy
  !
  PCTime-6 timezone clock
  PCTime of summer time clock day April 6, 2003 02:00 October 26, 2003 02:00
  IP subnet zero
  IP cef
  No dhcp use connected vrf ip
  DHCP excluded-address IP 192.168.7.1 192.168.7.19
  DHCP excluded-address IP 192.168.7.70 192.168.7.254
  !
  IP dhcp pool sdm-pool1
  import all
  network 192.168.7.0 255.255.255.0
  router by default - 192.168.7.1
  DNS-server 68.238.96.12 68.238.112.12
  !
  !
  inspect the IP name DEFAULT100 cuseeme
  inspect the IP name DEFAULT100 ftp
  inspect the IP h323 DEFAULT100 name
  inspect the IP icmp DEFAULT100 name
  inspect the IP name DEFAULT100 netshow
  inspect the IP rcmd DEFAULT100 name
  inspect the IP name DEFAULT100 realaudio
  inspect the name DEFAULT100 rtsp IP
  inspect the IP name DEFAULT100 esmtp
  inspect the IP name DEFAULT100 sqlnet
  inspect the name DEFAULT100 streamworks IP
  inspect the name DEFAULT100 tftp IP
  inspect the tcp IP DEFAULT100 name
  inspect the IP udp DEFAULT100 name
  inspect the name DEFAULT100 vdolive IP
  synwait-time of tcp IP 10
  IP domain name cods.com
  name of the IP-server 68.238.96.12
  name of the IP-server 68.238.112.12
  property intellectual ssh time 60
  property intellectual ssh authentication-2 retries
  !
  !
  Crypto pki trustpoint TP-self-signed-437228204
  enrollment selfsigned
  name of the object cn = IOS - Self - signed - certificate - 437228204
  revocation checking no
  rsakeypair TP-self-signed-437228204
  !
  !
  TP-self-signed-437228204 crypto pki certificate chain
  certificate self-signed 01
  30820254 308201BD A0030201 02992101 300 D 0609 2A 864886 F70D0101 04050030
  2 060355 04031325 494F532D 53656 C 66 2 AND 536967 6E65642D 43657274 30312E30
  69666963 34333732 32383230 34301E17 303731 30313632 33333131 0D 6174652D
  395A170D 2E302C06 1325494F 03550403 32303031 30313030 30303030 5A 303031
  532D 5365 6C662D53 69676E65 4365 72746966 69636174 652 3433 37323238 642D
  06092A 86 4886F70D 01010105 32303430 819F300D 00308189 02818100 0003818D
  BF73E16C 24A3FB0B A44C83C8 45ACEC75 163C2F0A 87836F7F A43FEB72 0EF26AFA
  C7F35ED6 CBCC6853 5E82B0A6 1FD8020B F3630023 AB30B870 B3155EE6 86988910
  4ACF5121 1CBFF4DC B705DF1E 5D0D698F 06493 D 3DD8D036 42 FE450D21 E26A4DAF
  CE6BA806 81A9F451 0246698E DA7B49E3 160F115C E1104FA9 31FA3C15 CD 782 279
  02030100 01A37E30 7C300F06 03551 D 13 0101FF04 05300301 01FF3029 0603551D
  20821E63 11042230 6F64732E 6F666472 63697479 6E677370 69707069 72696E67
  732E636F 6D301F06 23 04183016 24 D 77493 80142FA3 03551D 52CF7094 B847B6EB
  1385E2E5 0F3A301D 0603551D 0E041604 142FA324 D7749352 CF7094B8 47B6EB13
  85E2E50F 3A300D06 092 HAS 8648 01040500 03818100 076EE499 12F46D79 86F70D01
  375B7EA6 C9279DA4 B32723B5 908C9FB8 D42CB978 BB24A8FE 73579A3D CA 5130, 87
  B7716644 7E13710D C6E6360C D0A36F7B F62540E2 0C33523B E50396B9 2EF66FA7
  56519E62 E55EAF3C E1D9BEC9 3AE67B59 75E61F06 B649E90A 2798F755 7A020F0A
  F8BDABFA 1EE37B6A A918560D DA45AD70 801BC66E 94D1468E
  quit smoking
  username privilege 15 secret $5 1jgO$sGD@#l4yTtLtYoEZbh/Wl steal551.
  !
  !
  door-key crypto vpn_ddaus
  pre-shared key address 0.0.0.0 0.0.0.0 - key stealthfortyfor5
  door-key crypto vpn_rmlfk
  address of pre-shared-key 205.30.134.22 key stealthfortyfor5
  !
  crypto ISAKMP policy 10
  md5 hash
  preshared authentication
  Group 2
  !
  crypto ISAKMP policy 30
  BA 3des
  preshared authentication
  Group 2
  invalid-spi-recovery crypto ISAKMP
  ISAKMP crypto keepalive 20
  !
  Configuration group isakmp crypto VPNRemote client
  key ConnectNow45
  pool ippool
  ISAKMP crypto vpnclient profile
  VPNRemote identity group match
  client authentication list for / remote
  Remote ISAKMP authorization list
  client configuration address respond
  Crypto isakmp CODS_DDAUS profile
  key ring vpn_ddaus
  function identity address 0.0.0.0
  Crypto isakmp CODS_RMLFK profile
  key ring vpn_rmlfk
  function identity address 205.30.134.22 255.255.255.255
  !
  !
  Crypto ipsec transform-set esp-3des esp-sha-hmac RIGHT
  !
  Crypto-map dynamic dynmap 10
  Set transform-set RIGHT
  vpnclient Set isakmp-profile
  Crypto-map dynamic dynmap 12
  Set transform-set RIGHT
  CODS_DDAUS Set isakmp-profile
  !
  !
  MYmap 1 ipsec-isakmp crypto map
  defined by peer 205.30.134.22
  Set transform-set RIGHT
  CODS_RMLFK Set isakmp-profile
  match address CODS_to_RMFLK
  map mymap 65535-isakmp ipsec crypto dynamic dynmap
  !
  Bridge IRB
  !
  !
  interface Loopback10
  IP 1.1.1.1 255.255.255.0
  !
  ATM0 interface
  no ip address
  route IP cache flow
  No atm ilmi-keepalive
  DSL-automatic operation mode
  !
  point-to-point interface ATM0.1
  Description $FW_OUTSIDE$ $ES_WAN$
  Check IP unicast reverse path
  inspect the DEFAULT100 over IP
  NAT outside IP
  IP virtual-reassembly
  PVC 0/35
  aal5snap encapsulation
  !
  Bridge-Group 2
  !
  interface FastEthernet0
  !
  interface FastEthernet1
  !
  interface FastEthernet2
  !
  interface FastEthernet3
  !
  interface Dot11Radio0
  no ip address
  no ip-cache cef route
  no ip route cache
  !
  encryption vlan 1 tkip encryption mode
  !
  SSID tsunami
  VLAN 1
  open authentication
  authentication wpa key management
  Comments-mode
  WPA - psk ascii 7 14231A0E01053324363F363B36150E050B08585E
  !
  base speed - 1.0 2.0 basic basic-5, 5 6.0 9.0 basic-11, 0 12.0 18.0 24.0 36.0 48.0 54.0
  root of station-role
  !
  interface Dot11Radio0.1
  encapsulation dot1Q 1 native
  no ip route cache
  no link-status of snmp trap
  No cdp enable
  Bridge-Group 1
  Bridge-group subscriber-loop-control 1
  Bridge-Group 1 covering-disabled people
  Bridge-Group 1 block-unknown-source
  No source of bridge-Group 1-learning
  unicast bridge-Group 1-floods
  !
  interface Vlan1
  Description $ETH - SW - LAUNCH, INTF-INFO-HWIC $$ $4ESW $FW_INSIDE$
  no ip address
  IP tcp adjust-mss 1452
  Bridge-Group 1
  !
  interface BVI1
  Description $ES_LAN$ $FW_INSIDE$
  192.168.7.1 IP address 255.255.255.0
  IP nat inside
  IP virtual-reassembly
  route IP cache flow
  IP tcp adjust-mss 1412
  !
  interface control2
  IP 70.14.49.134 255.255.255.0
  NAT outside IP
  IP virtual-reassembly
  crypto mymap map
  !
  local pool IP 10.10.10.1 ippool 10.10.10.254
  IP classless
  IP route 0.0.0.0 0.0.0.0 70.14.49.1
  !
  IP http server
  local IP http authentication
  IP http secure server
  IP http timeout policy slowed down 60 life 86400 request 10000
  overload of IP nat inside source list 133 interface control2
  !
  CODS_to_RMFLK extended IP access list
  IP 192.168.7.0 allow 0.0.0.255 192.168.1.0 0.0.0.255
  !
  recording of debug trap
  access-list 1 permit 192.168.7.0 0.0.0.255
  access-list 100 remark self-generated by the configuration of the firewall Cisco SDM Express
  Access-list 100 = 1 SDM_ACL category note
  access-list 100 deny ip 70.14.49.0 0.0.0.255 any
  access-list 100 deny ip 255.255.255.255 host everything
  access-list 100 deny ip 127.0.0.0 0.255.255.255 everything
  access ip-list 100 permit a whole
  access-list 101 permit ip 192.168.7.0 0.0.0.255 192.168.3.0 0.0.0.255
  access-list 133 deny ip 192.168.7.0 0.0.0.255 192.168.1.0 0.0.0.255
  access-list 133 deny ip 192.168.7.0 0.0.0.255 10.10.10.0 0.0.0.255
  access-list 133 deny ip 192.168.7.0 0.0.0.255 192.168.10.0 0.0.0.255
  access-list 133 deny ip 192.168.7.0 0.0.0.255 192.168.3.0 0.0.0.255
  access-list 133 allow ip 192.168.7.0 0.0.0.255 any
  not run cdp
  mymap permit 10 route map
  corresponds to the IP 111
  set ip next-hop 1.1.1.2
  !
  !
  control plan
  !
  Bridge Protocol ieee 1
  1 channel ip bridge
  Bridge Protocol ieee 2
  IP road bridge 2
  connection of the banner ^ CAuthorized access only!
  Unplug IMMEDIATELY if you are not an authorized user. ^ C
  !
  Line con 0
  no activation of the modem
  telnet output transport
  line to 0
  telnet output transport
  line vty 0 4
  privilege level 15
  transport input telnet ssh
  !
  max-task-time 5000 Planner
  Scheduler allocate 4000 1000
  Scheduler interval 500
  end

  Hello

  Can you try to remove the IMPORT ALL of the dhcp pool

  RES
  Paul

  Sent by Cisco Support technique iPad App

• DHCP Snooping

  Scenerio:

  As part of a modernization project of tech in a big campus and because of several problems caused by users (l) connect the routers on the network and causing DHCP issues, I'm looking to turn on DHCP snooping. During the tech switches access update will be updated first and then the kernel. The new access switches are 4510R + E/Sup7, running the latest IOS XE base license and just passing through. New carrots are 6509 Sup 720's configured as a cluster VSS, manage all routing for VIRTUAL local area networks and have the statements of support IP. The DHCP server which takes care of all the VLAN is a Windows 2008 server that is directly connected to the base.

  I also read all the info I could find on DHCP snooping, but I'm still a little fuzzy on if it changes the way that the DHCP server handles requests.

  Issues related to the:

  • Because the access switches pass only, they only need monitoring DHCP enabled (in the world and on VIRTUAL local area networks) and their uplinks to the core set as being approved, right? In particular, they only declarations of support IP or Layer-3 interfaces for all of their VIRTUAL local networks, right?
  • While I understand that DHCP snooping will be ineffective if it is not lit on the kernel, there is no reason I can't deploy it first to the access layer without touching the basic configurations to avoid large amounts of documents of change control, right? Then, when the kernel is put at level and DHCP snooping successfully activated that will work.
  • I got that on the layer to access the switches uplink to the core are approved, but I'm not 100% on the question of whether the same interfaces are approved on the carrots. I don't think but want to be sure. Carrots of course trust the real interface on that server DHCP is plugged
  • The most confusing part is all the stuff from the Option-82. As near as I can tell its option for the server to use the information from the Option-82. I think that if all I do is enable DHCP snooping on worldwide and on the right VIRTUAL LANs the DHCP relay between the core and the DHCP server will continue to work as it is today, is that correct?

  Is there really this traps or in my case I really just need to turn it on in the world and by vlan, trust the uplinks on the access switches and the DHCP server on the kernel interface and call it a day?

  Thank you

  Nathan Spitzer

  SR Network Communications analyst.

  Lockheed Martin

  Hello Nathan,.

  Given that the access switches are only switching, they only need DHCP snooping turned on (both globally and on the VLANS) and their uplinks to the core set as trusted, right?

  Fix.

  In particular they dont need IP helper statements or layer-3 interfaces for all of their VLANS, right?

  Fix. The statement of support ip address would only be necessary if switches performed routing inter - VLAN and the DHCP server is located in a VLAN different.

  While I understand that DHCP snooping will only be marginally effective if it is not turned on on the core, there is no reason I cannot deploy it first at the access layer without touching the core configurations to avoid large amounts of change-control paperwork, right? Then when the core is upgraded and DHCP snooping properly enabled it will work. 

  To my knowledge, the opposite is true. DHCP Snooping is a service of access protection layer - is it not in the core of the network. It has nothing to protect in the kernel once DHCP messages have beein properly disinfected at the edge of the network. For some inexplicable reason, many people think that the DHCP Snooping should be enabled on the network. The fact is that the DHCP Snooping protects against

  • DHCP messages are sent to ineligible devices
  • Ineligible devices posing as DHCP servers

  From this it naturally follows that it is the limit of the network, or the layer of access, where such protection is the most effective. So in your case, I believe that the activation of the DHCP Snooping only on the access layer is actually what you want to do.

  I got that on the access layer switches the uplinks to the core are trusted, but I am not 100% on whether the same interfaces are trusted on the cores. I dont think so but want to be sure. Of cource the cores do trust the actual interface the DHCP server is plugged in on

  If you enable the DHCP Snooping on the basic features and uplink between the access switches and core would have to be configured as confidence both on the basic switches and access. Otherwise, the base ports would pass DHCP messages received from customers because the access layer switches running DHCP Snooping insert DHCP Option 82 in the DHCP messages sanitized and ports untrustred delete all DHCP messages including 82 of the present Option.

  2960 Configuration Guide to

  http://www.Cisco.com/en/us/docs/switches/LAN/catalyst2960/software/release/12.2_55_se/configuration/guide/swdhcp82.html#wp1078853

  The switch removes a DHCP packet when one of these situations occurs:

  • Comes from a packet to a DHCP server, for example a DHCPOFFER, DHCPACK, DHCPNAK or DHCPLEASEQUERY package, outside the network or firewall.

  • A packet is received on an interface that is not reliable, and do not match the source MAC address and hardware address of the DHCP client.

• The switch receives a message DHCPRELEASE or DHCPDECLINE with a MAC address in the DHCP snooping database binding, but the information in the database of linking interface does not correspond to the interface on which the message was received.

• A DHCP relay agent sends a DHCP packet that includes a relay agent IP address which is not 0.0.0.0 or relay agent transmits a packet that includes information of option-82 to an untrusted port.

As I have indicated, however, I personally discourage running DHCP Snooping on the basic devices - I see no reason for this. Please correct if I am wrong!

The most confusing part is all the Option-82 stuff. As near as I can tell its optional for the server to use the Option-82 information. I believe that if all I do is turn DHCP snooping on globally and on the right VLANS the DHCP relaying between the core and the DHCP server will continue working just like it is today, is that correct?

LOL, my favorite on the DHCP Snooping things is the Option 82 interesting how much this topic brings confusion...

The Option 82 was created to provide DHCP relay agent the ability to identify itself and the customer who sent the original message from DHCP unmodified. The DHCP server can then use this information to perform certain policies of customer trust. The format of the Option 82 is not strictly specified, only its basic structure is fixed. You can read more on this and the whole reason to be in the RFC 3046. One of the key points to remember here, however, is that the DHCP server may or may not recognize the Option 82, but apart from that, to copy the value of the Option 82A received in the message to a DHCP client for all its replies sent to this client.

DHCP Snooping uses the Option 82 differently. He didn't expect and doesn't require that the DHCP Server includes the Option of 82 or manages a special way. The Option 82 is inserted by switches access performing DHCP Snooping and it contains two important parts:

• The Circuit ID that identifies the port to which the client is connected (VLAN and the location of the physical port in a switch)
• The remote ID that identifies the access switch to which the client is connected (by the MAC address of the switch)

See http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_55_se/configuration/guide/swdhcp82.html#wp1105589

Now, when an access switch performing DHCP Snooping receives a message from DHCP client on an untrusted port, this will happen:

• The switch will insert the 82 Option in the message of the DHCP client. The Option 82 will identify the specific switch and the port to which the client is attached
• The switch will forward the DHCP message according to its MAC address of destination (i.e. in a completely normal way)
• The server receives the DHCP message containing the Option 82. It is not relevant for DHCP Snooping if the server takes into account the value of the Option 82. However, when the server replies, it will insert the original value of the Option of 82 to the answer.
• Access switch will finally receive the DHCP response. Looking at the Option 82, he knows exactly in which port is the message transmitted to the customer - and only the customer - even if the answer was broadcast!

Note that the Option 82 contributes enormously to identify exactly the access switch and its port where the client is attached. If other switches with DHCP Snooping has received this DHCP message (in reason of the flood or address broadcast requested by the client), they would pass this message because they understand once glancing at the 82 Option that the customer is attached elsewhere. The 82 Option allowing to ensure DHCP communication between a particular client and the DHCP server doesn't leak not to other customers.

There is a hunt for witches, associated with the Option 82. A switch run DHCP Snooping inserts the Option 82 messages DHCP clients. However, each DHCP message contains a field named GIADDR where the IP address of the relay agent is registered, where the DHCP message was relayed. Clearly, when a DHCP message goes through a switch DHCP Snooping, it is not relayed (drawn from one VLAN and rerouted to another), so an access switch does not change the GIADDR that remains set to 0.0.0.0. However, at least the implementation of server DHCP Cisco IOS performs a validation on a test received DHCP messages and it drops DHCP messages containing the Option 82, but which the GIADDR field is set to 0.0.0.0 (i.e. unitialized). This can be seen in the output of the debug ip dhcp server packet :

Router# debug ip dhcp server packet

*Sep 9 01:59:40: DHCPD: inconsistent relay information.

*Sep 9 01:59:40: DHCPD: relay information option exists, but giaddr is zero

Under normal circumstances, such a mental health check makes sense - how is it that a DHCP message contains the Option 82 (i.e. the Relay Agent Information Option DHCP) when there is no DHCP relay identified in the GIADDR? However, with DHCP Snooping on the access layer switches, DHCP messages are normal and expected. Therefore, it is essential to disable this check of mental health on the Cisco box that is running the DHCP server configuration using global ip dhcp relay confidence all information or only is selected routed (i.e. L3) interfaces with command level interface ip dhcp relay reliable information.

To summarize:

• The 82 Option is A Good Thing (TM) because it allows to deliver DHCP messages only to the client for which they are intended. Any suggestions to disable the insertion of the Option 82 on access DHCP Snooping Switches are useless 82 Option is inserted by DHCP Snooping Switches in DHCP messages by default - no additional configuration is necessary.
• Through the easiest way - when you deploy DHCP Snooping, does not initially change anything about the Option 82. Make sure that your customers can receive their config IP via DHCP. If yes then there is nothing to resolve. If not, go further.
• If you run a DHCP server on a Device IOS base (router, switch), you may need to use the command ip dhcp relay information confidence-everything (global config) or ip dhcp relay reliable information (level interface) to allow the DHCP messages with the Add Option 82 and unitialized field GIADDR to be accepted. These commands are required only on the device where the DHCP server is running, not on the access layer switches. You may want to first perform debugging as I suggested previously, and only if you see that packets are dropped, add these commands to the configuration.
• I don't know if these commands should be added also to a DHCP relay function efficient switch - I can check that tomorrow in a laboratory.
• If you are using another DHCP server you have to try experimentally whether happy with the DHCP messages with 82 Option present and unitialized GIADDR field

Sorry for the long answer... I hope that I do not bore you to death. We invite you to ask for more! I'll try to be more concise next time

Best regards

Peter

• ThinkServer RD630 black screen

  Hi all

  I've been set a ThinkServer RD630 to present itself as a storage array. I was able to configure the RAID array, install Server R2 2012 and connect. However, I lived with DHCP issues. To try to solve this problem, I have checked the BIOS for all the 'hard' parameters and had not found any. After reboot, I was presented with a black screen with no other information. I tried to reset the BIOS, but to no avail (server never shows anything on the attached KVM). I also have basic troubleshooting and various other devices connected. It is clear that the USB ports are turned, but none of the devices are never activate which would indicate the server makes to the BIOS. Any thoughts?

  FYI: Solved my problem. Resetting jumpers CMOS brought me back in place and running!

• 2012 DNS server settings

  DNS issues: Installed server 2012 and DNS/DHCP issue with IP address of my network, but having routing problems.

  -Some PC may well navigate the Internet

  D ' others can pull up Google and that's it, they get search results, but can click on links, everything turns and resolves to any server.

  -Some can ping other PC via IP and host name, but application cannot find the other PC via hostname

  Question:

  -Can we go directly from a cable modem the domain controller, or a device to bind a small router (small businesses) to translate my external IP address internally?  Company would use a camera ASA or NSA...?

  Advice is appreciated!

  My configuration:

  DLink WAN

  DLink LAN

  DNS server of 2012

  DHCP

  This issue is beyond the scope of this site and must be placed on Technet or MSDN

  http://social.technet.Microsoft.com/forums/en-us/home

  http://social.msdn.Microsoft.com/forums/en-us/home

• Connection through a switch?

  I have a WRT54G V8 router that I want to spend down for better reception.  I want to connect it via my switch EZXS55W V4.2 but I can't seem to make it work.  Do I have to change the settings of the router or is - same not possible?

  Modem high speed---> switch---> router

  michaeloquence wrote:

  I have a WRT54G V8 router that I want to spend down for better reception.  I want to connect it via my switch EZXS55W V4.2 but I can't seem to make it work.  Do I have to change the settings of the router or is - same not possible?

  Modem high speed---> switch---> router

  You can't the front switch the router because it wouldn't give the DHCP issued IP address of this way. The indicated above guy in the correct way to do it.

• WRT160N works is not in a situation of LAN - LAN

  WRT160Nv3 FW v3.0.03

  I made this a million times over 1 million different routers and never once have trouble like that. Cannot know what is the problem for the life of me. I simply add a WRT160N at our company as an access point network, not a router. I have a dozen WRT54G around facility HERE exactly in the same way and they all work very well. I have connected a normal LAN cable from the wall to the WRT160N #1 LAN port. I am sure that this cable in the wall works very well, I tested it with a laptop and the laptop gets an address IP DHCP issued since our DHCP in Windows Server 2003 very well. The laptop can browse the internet and local network without problems. On the basic configuration of the WRT160N page I put the automatic/DHCP Internet connection, set the IP address of network for 192.168.1.222 configuration to match our LAN, which is 192.168.1.0/24. I put the subnet mask of 255.255.255.0. I disabled the DHCP server. Under routing Advance I have disabled NAT, RIP off and none of the static routes. In the wireless settings I created an SSID, Wireless N only Mode value (I want this broadcasting only N, not G/B), width of the channel the value Auto and auto channel. The SSID broadcast is turned on. Is wireless security mode WEP with 128-bit encryption and key 1 contains our company WEP key. All the other settings on all tabs remain their default, the out-of-the-box settings.

  Very well, the router broadcasts the SSID. It goes not to the long DHCP clients, and perhaps has not managed their requests to our DHCP server, I'm not sure. In any case, normally with this configuration you just connect a LAN cable to the wireless router's LAN port and're you good to go. Not the case here, for some reason any. Nobody can join this network because the router is not passing along data DHCP. Administration-> Diagnostics, I can ping other devices on our network local but cannot get anywhere outside our local network. The status page shows all zeros for gateway/subnet/IP in the Internet access section.

  What I'm doing wrong here? Or is it just broken router? We have tried resetting to factory default, we tried to upgrade the firmware, everything that we can think of and nothing works.

  TIA

  You tried all possible measures to connect the Linksys router.

  If it still doesn't work then I think you need a new router.