PeraHoman
asked on
BGP question, same ASN different locations
To sum:
All devices are located at the same site, but are still physically apart.
R3/Core3 need to be configured as a standalone network, it use to be part of 172.16.5.0/24, but is going to be torn down after a few days. R3/Core3 use to be "core 2" Core 2 is being upgraded for now, later core 1.
This is a physical move, and I'm trying to refresh the network while we are moving, but am limited to refreshing only half the network for now. This move can't be done in a single move, and will take a few days, so all the workstations at R3 will connectivity to the MPLS backbone until everything is moved into R2/Core2.
My question is: Can I advertise two different networks from the same ASN 5? Let's say filtering is in place, so don't worry about that. I just want to know if there are going to be any issues. I don't think there will be, but I'm not certain. I'm thinking when I do a show ip bgp, it'll show both prefixes but different next-hops?
Thanks
ASKER
let me add some more info.
-R1 and R2 will be ibgp neighbors. r3 will not be an ibgp neighbor with r1 or r2. it'll be a stand alone. i could make r3 belong in a new asn '4', but im wondering what would happen if i left it in the same asn 5. this will only be temporary (less than 15 hours), and r3/core3 will be decommissioned. im guessing if r3's network needed to reach r2/r1 network then ebgp 'split herizon' would drop those packets coming from r3 to r1/r2 and visa versa.
-R1 and R2 will be ibgp neighbors. r3 will not be an ibgp neighbor with r1 or r2. it'll be a stand alone. i could make r3 belong in a new asn '4', but im wondering what would happen if i left it in the same asn 5. this will only be temporary (less than 15 hours), and r3/core3 will be decommissioned. im guessing if r3's network needed to reach r2/r1 network then ebgp 'split herizon' would drop those packets coming from r3 to r1/r2 and visa versa.
As long as R3 is not interconnected to the network to which R1 and R2 are -- leaving it in the same ASN without iBGP is fine. Just be sure to allow your own AS in within your BGP configurations.
ASKER
Just be sure to allow your own AS in within your BGP configurations.
Can you provide an example?
Thanks!
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If you want to advertise more than one prefix, then the answer is yes.
Or, do you want to create another segment of the network that runs under the same ASN? The answer is also yes:
You will either want a full iBGP mesh (small network) or route reflectors (large network) for all BGP speaking devices in your network.
The exception is if you treat these as distinct networks using the same ASN. Then you have to configure BGP to allow traffic that originates from outside that network but under your ASN into that network.