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Re: BGP, ebgp-multihop and multiple peers
- From: Truman Boyes
- Date: Tue Aug 26 21:41:59 2008
Steve,
You ask a very good question because I have seen some providers embark
on the multiple loopback approach for numerous reasons. I suggest a
single loopback per routing-instance whenever possible. The cost
savings in OSS and integration in routing configurations with a single
repeatable block of configuration per peer/peer group is far more
beneficial than some corner case technical benefit of having multiple
loopback addresses.
I have been forced for other feature support to deploy multiple
loopback interfaces, but have always opted to keep all EBGP peering
with a single loopback interface per routing-instance.
Kind regards,
Truman
On 26/08/2008, at 7:48 PM, Steve Bertrand wrote:
Hi everyone,
This question comes after likely overlooking an IETF document or BCP
that describes what I'm after. Given that I am looking for advice
from someone who is more experienced operationally in this regard
than me, and that this technically is an implementation-neutral
question, I wanted to ask here.
Taking one router I have as an example, I have four IPv6 BGP peers
(two are for true routing, the other two for route server projects),
and five IPv4 BGP peers. Two of the v4 peers are Cymru for BOGONS,
the other three are purely outbound to route server projects. All
five v4 peers are ebgp-multihop.
I'm looking for advice on the configuration of the peers with ebgp-
multihop (IPv4).
I have a reserved block carved out of my allocation specifically
for /32s on loopbacks, and when I light up a new peer, I configure a
new looopback interface for that peer, and subsequently give it the
next available IP from the reserved /32 block.
There are numerous drawbacks to doing it this way... waste of IPv4
addresses, additional keystrokes on the router for interface config,
documentation, expanded margin for error et-al.
There are a few benefits to doing it this way (IMHO), but I see
obvious benefits of using a single loopback interface and single IP
for ALL of these multihop peers. Before I state good/bad, or get any
wrong idea in my head, I'd like to ask the real experts here which
way they would/do this type of thing, and why.
- single loopback/single IP for all peers, or;
- each peer with its own loopback/IP?
Thanks,
Steve
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