Solved: Re: How to have symmetric traffic in BGP Multihomed network

S. B · ‎07-29-2021

Hi,

Is there any solution (except using PBR) for controlling the outgoing traffic to the service providers from our side?

We want each buildings send/receive traffic go through each provider, while all providers can act as backup for others.

For controlling the incoming traffic, its easy.

Just advertising the specific/24 of the building + the complete /22 address, to each provider.

How about the outgoing traffic?

As we want it symmetric, so each building will send their own traffic from their specific service provider

If no solution, maybe with putting each customer/building in a vrf and the 3 service providers in a shared vrf? and with import/export? (makes it complicated)

Or maybe sending the traffic from each building to the correct router, and then controlling the outgoing traffic with BGP attributes?(but seems still in some failover scenarios, requires PBR)

Thanks

Richard Burts · ‎07-29-2021

Thanks for explaining your reservations about PBR. While it is true that on some switches the PBR is done in software and so does drive up CPU. But there are now many switches for which PBR is done in hardware. See this link for an example of that

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/pbroute.pdf

and this link to a discussion in the community about hardware processing of PBR

https://community.cisco.com/t5/switching/does-pbr-in-vrf-is-hardware-switched-on-cat6509-sup720-3b/td-p/1500388

It is probably true that multiple failure scenarios would complicate the implementation of PBR. I believe that those multiple failure scenarios would also complicate the vrf approach.

I am not sure but I believe the vrf approach would not accomplish what you want. I am not aware of other solutions that would do it but wonder if perhaps something like SDWAN might provide a solution.

I do not have performance information about the 3850 or the 3064 in processing PBR. Perhaps someone else in the community might have that information and if so I hope they jump into this discussion.

HTH

Rick

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