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New Member

IP route-cache flow over WCCP

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


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

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.







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 ..

  • Wide Area Application Services (WAAS)
New Member

Re: IP route-cache flow over WCCP


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?



New Member

Re: IP route-cache flow over WCCP

HI Tom,

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

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