BGP vs OSPF

[winston123]

Hello everyone

Question: i have bgp running on a layer3 switch to provider A, and now im trying to configure ospf with /30 and /32 loopback ips  to provider B's mpls vpn network thru a  cat5 handoff. Can I configure ospf on that switch if its already running bgp, wont that interfere?

Your answer will be appreciated.

Thanks

Winston

[Giuseppe Larosa]

Hello Winston,

you can run BGP and OSPF on the same device but all depends on what you want to achieve:

if the BGP session with provider A is an eBGP session the routes learned on it are preferred for their lower admin distance (20) in comparison to OSPF (110).

So if you want to use the connection with ISP B as a secondary path to be used when link to ISP A fails you are fine.

Things are more difficult if you would like to do the opposite and very difficult if you would like to load balancing ( almost impossible).

Finally, if you are learning different IP subnets on the two links to different remote sites you may be fine or you may need to move route information between the two routing protocols.

This final need depends if the local site/switch has to route between the different subnets learned from the two links/SPs

Hope to help

Giuseppe

[winston123]

Thanks a lot Giuseppe for the information. I does help a lot, i will use ospf for a trial only with provider B so i should be fine.

Regards

[Jason Masker]

You can configure both on the router.  They will not interfere on the wire because they are completely different protocols.  Also this is a common scenario as BGP is an external gateway protocol and OSPF is for internal use. So it is not common to receive a route via BGP and advertise it back in to OSPF or visa versa.

[winston123]

Thanks a lot Jason for the quick answer and for the info.

[winston123]

Hello Jason,

Do you happen to have or direct me to a config of OSPF and loopback interface on  layer3 switch (WS-C3560G-24TS) using VLAN. I know how to do on a router with Serial and ethernet interface, but not on a switch where i have to use the Vlan interface to assing my /30 IP.

Thanks much in advance,

Winston