Change routing path

[Martin Mraz]

Hello,

I need to change routing path through the router. Topology is this:

Normally traffic goes: from PC -> E1 -> E4 -> server. Traffic needs to flow like this: from PC -> E1 -> E2 -> E3 -> E4 -> server. Is there a way to do this? I tried PBR with no luck. The bridge has no IP address from router`s point of view.

[John Blakley]

It's a little difficult to tell what you're wanting to do. Is this the way everything is really connected? If there isn't an address on the bridge, you won't have anything to route to and the router will see whatever subnets it holds as connected routes. You may be able to bridge the connection between e1-2 and bridge between e3-4. Can you post the config of the router?

HTH,
John

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[Martin Mraz]

Hello John,

this scenario is mostly in my head right now. E1 and E4 must be routed ports. With E2 and E3 I am not sure. The idea is to divert interesting traffic through the bridge and analyze it there. The picture is simplified, there are routers (ASR) instead of pc and server in production.

[John Blakley]

Ah, I got it now. You could try to bridge them although I've never done it for this purpose. You could try something like this:

bridge irb

int e1

bridge-group 1

int e2

bridge-group 1

int e3

bridge-group 2

int e4

bridge-group 2

int bvi1

ip address that's on e1 now

int bvi2

ip address that's on e4 now

bridge 1 protocol ieee

bridge 2 protocol ieee

bridge 1 route ip

bridge 2 route ip

Like I said, I'm not sure if this will work but it would be a good lab experiment.

HTH,
John

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[milan.kulik]

Hi,

what about following trick:

Put interfaces E3 and E4 to another VRF.

Use the same subnet  for E2 and E3 addressing.

Create a static route for the server pointing to E3 IP address.

Create a static route  withing the new VRF for the PC pointing to E2 IP address.

When E2 and E3 ports would be connected via a bridge, following routing should follow:

Packets would be sent from the PC with the server destination address and forwarded  from E2 to E3 MAC address (E3 would reply to ARP request sent from E2 as believing to be within the same subnet).

E3 would receive it and forward to the server based on the routing within its VRF.

Returning  traffic should be routed similar way.

HTH,

Milan

[John Blakley]

I labbed this up and it doesn't work. The problem is that the routes are still connected routes. I tested this by shutting down one of the links that was bridged to the switch and the router still passes traffic but nothing gets copied to the bridge. The router is just routing between interfaces and not sending the traffic across.

HTH,
John

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