How to solve the problem of ARP cache on CORE sw 6506 ?

Dipesh Patel · ‎07-07-2008

Dear Sir,

We have problem of ARP cache on Core sw 6506 . Topology for this is as per attachment.

Problem is : The pcs which are turned off for 3- 4 hour can not communicated. from this PCs some of Devices and some of Servers also can not pinging . Some of PCs have an error : Reply from x.x.x.x(Gateway):TTL expires in transit.

Now if i ping this effected PC from MSFC than its works well. Before it i have checked sh arp | i x.x.x.x ( PC Ip address ) than I can not find it. But After pinging from MSFC i can found in ARP list. So I suspect it is due to ARP cache.

I had tried to clear all arp but the problem is still exist.

This problem is in all PCs with static IPs as in PCs with DHCP - Continuous ly communicated so not isolated.

As a temp Solution we have rebooted nboth the core sw and removed one sup card from both the end.

But reboot Sw is not the solution.

So pls help me to solve the problem :

Pls give me the action plan to solve - to troubleshoot the problem.

I am here attaching the Dia.

Pls help me soon.

Dipesh Patel · ‎07-07-2008

Dear all,

Pls reply soon ...............

Giuseppe Larosa · ‎07-08-2008

Hello Patel,

I'm starting to wonder if what you are doing could be done in a simpler way.

In another thread you explained that you have two MSFCs in each chassis and only one is Active and one is Standby (this is SRM).

Here, you are building HSRP groups between the four MSFCs but only two of them at each time can talk with the outside world.

the standby MSFC has its configuration synchronized with the active one but it is not visible outside. For example it cannot use a tacacs+ server for AAA authentication but only a local account allows to access it.

It looks like that if a PC performs an ARP request the result is different then when you do a ping from the MSFC.

ARP request is sent to a broadcast, ARP reply is sent to the ARP request's source MAC address.

in your sh standby for one HSRP group you see an active, a standby only.

see the following link

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/release/notes/OL_4164.html

are you using SSO and SRM together ?

hope to help

Giuseppe