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ARP replies from HSRP gateway lost over wireless

We have 2 access switches (3750s) that are both attached to a pair of Nexus 5548UPs with L3 cards over VPCs.  Access switch (AC1) terminates our 4402 WLC.  The WLC services 4 WLANs and connects to the access switch with a single trunked port.  Access switch 2 (AC2) terminates an 1131AG lightweight AP.  The WLAN is 10.1.1.0/24 on VLAN 300.  Router 1 (R1) VLAN 300 IP is 10.1.1.2.  Router 2 (R2) VLAN 300 IP is 10.1.1.3.  R1 is the active router for VLAN 300.  The standby IP for VLAN 300 is 10.1.1.1.  The VPCs between both access switches and the router pair are functioning correctly and trunks are wide open (no pruning).

Wireless clients get a DHCP address from a server on another VLAN.  Those addresses get handed out just fine.

Wireless clients can ping 10.1.1.3 (R2).  They cannot ping 10.1.1.1 (standby address) or 10.1.1.2 (R1). 

I took captures from the WLC and I see the ARP requests and replies from wireless clients to their gateway (10.1.1.1).  I took another capture directly from the wireless clients themselves.  From there, we see the ARP requests, but never the replies.  If I create a static ARP entry on the client, it can ping the gateway just fine.

Any ideas? 

Thanks in advance.

--steve

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5 REPLIES

Re: ARP replies from HSRP gateway lost over wireless

What version of code are you running on the 4400?  To my knowledge HSRP should work fine, but there were problems with GLBP in pre 7.0 code.

Can you post the config of the HSRP pair?

Steve

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
Community Member

Re: ARP replies from HSRP gateway lost over wireless

The 4402 code is embarassingly old:  4.0.217.0

R1

interface Vlan300

  ip address 10.1.1.2/24

  ip router eigrp Core

  hsrp 1

    preempt delay minimum 180

    priority 140

    timers  1  3

    ip 10.1.1.1

  ip dhcp relay address 10.2.1.10

  no shutdown

  description *Wireless

R2

interface Vlan300

  ip address 10.1.1.3/24

  ip router eigrp Core

  hsrp 1

    preempt delay minimum 180

    priority 130

    timers  1  3

    ip 10.1.1.1

  ip dhcp relay address 10.2.1.10

  no shutdown

  description *Wireless

Re: ARP replies from HSRP gateway lost over wireless

Interesting.  Are you able to reboot the WLC?

Steve

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
Community Member

ARP replies from HSRP gateway lost over wireless

The WLC has been rebooted recently.  I could reboot it again if I had a reason to think that was going to help. 

Re: ARP replies from HSRP gateway lost over wireless

Stephen:

It seems you need to use virtual IP address as a gateway for your WLAN clients.

I can see this:

Q. I connected my WLC to Cat6500 switches configured for routing, and I configured HSRP between these switches. However, I am now unable to reach other subnets through WLC. How do I resolve this issue?

A. When HSRP is in place, a virtual IP address and MAC address is usually configured for the HSRP group, which is used for routing. Hosts continue to forward IP packets to this consistent IP and MAC address even when one of the switches go down and change over to a standby device takes place. Complete these steps in order to resolve the routing issue:




  1. Make sure the virtual IP address is configured as the default gateway on the WLC.Note: Certain earlier versions of WLC do not forward packets to HSRP MAC address, which results in failure to route packets. Upgrade the WLC in order to resolve this issue.
  2. Make sure the virtual interface on the WLC is properly configured. For more information on interfaces, refer to the Configuring Ports and Interfaces section of the WLC Configuration Guide.

Reference: Wireless LAN Controller (WLC) FAQ

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