IP route-cache flow over WCCP

vsraghav123 — Tue, 26 Oct 2010 12:28:27 GMT

Hello All,

I have a query , we have enabled ip route cache flow on the main ATM IMA interface and we have few subinterfaces configured in it.While looking at the output of ip cache flow I see the source IP add & source interfaces to be different i.e. in the below example 172.18.96.0/22 is a subnet which resides behind AT0/IMA0.75 but I see this subnet as a source / destination IP through a different sub-interfaces.As per the network setup there is no other link for the other sub-interfaces to reach the mentioned subnet.

below is one sample output , we see lot of traffic as highlighted below

AT0/IMA0.776 172.18.96.115 Gi0/0.1 172.18.9.64 06 047D 0882 1 - In this example the mentioned IP should not reflect the source interface as Ima.776 rather it should b only IMA.75 as below.

AT0/IMA0.75 172.18.96.115 Gi0/0.1 172.18.9.64 06 047D 0887 1 - this is right information
AT0/IMA0.779 172.18.11.15 AT0/IMA0.75 172.18.96.186 06 0CF6 0050 1 - this is right inforamtion

configurations

interface ATM0/IMA0
no ip address
ip route-cache flow
logging event subif-link-status
load-interval 30
ima clock-mode common 0
ima differential-delay-maximum 150
atm vc-per-vp 1024
no atm ilmi-keepalive
end

we have these many subinterfaces.ATM0/IMA0.75 is the connection to hub site and the rest are the spoke sites connecting to this router lastly this router is the only transit to reach the hub router.

ATM0/IMA0

ATM0/IMA0.75

ATM0/IMA0.775

ATM0/IMA0.776

ATM0/IMA0.777

ATM0/IMA0.779

No routing issues as the route table looks completly good.

And today I disbaled WAAS ,removed WCCP redirect statement and the traffic flow was normal , would like to know why we see this kind of traffic flow ? Moreover we have seen this kind of traffic flow in different routers as well the common thing on all these routers are

1. Common physical link binded with multiple sub-interfaces

2. WCCP enabled

3. IOS 12.4 25c

Let me know if anyother information is required ..

Re: IP route-cache flow over WCCP

Thomas Jardin — Tue, 16 Nov 2010 15:24:32 GMT

Hello,

This is a bit of a theory, but I have an explanation if you have the WAE configured for "Egress-Method Negotiated-Return"

In that case the WAE returns the packet to the router in a GRE tunnel that has a destination IP of the Router ID IP. The GRE header is removed, then the router does a route lookup for the inside (true source IP) next hop interface. It then re-injects that traffic onto that interface and the packet is processed normally,

Or even more simply, is AT0/IMA0.776 the interface connected to the WAE?

Regards,

Tom

Re: IP route-cache flow over WCCP

vsraghav123 — Mon, 22 Nov 2010 08:31:18 GMT

HI Tom,

Thanks for your response and I have worked with TAC , it was identified as bug CSCti86131.

topic Re: IP route-cache flow over WCCP in Application Networking

IP route-cache flow over WCCP

Re: IP route-cache flow over WCCP

Re: IP route-cache flow over WCCP