At 08:00 05/02/2001 -0500, Eric Osborne wrote:
>
> >
> > /30s in iBGP? I checked the thread and didn't see where that was
> > mentioned.
>
>See above where Barry says "[/30s] would be advertised and generated into
>your iBGP". I'm not so sure I like this either, and I don't know of
>anyone who does this. I could be wrong, tho.
I missed that.
>He may have meant /30s as externals in your IGP (Barry?), but
>
>1) this is really only a concept that applies to OSPF, and
If we do a "redistribute connected" yes, but it is also possible to use
network statements and carry them as internals (using the new
passive-default passive to make all interfaces passive by default). I think
this is what he meant... ;-)
>As far as unnumbered, my .02 is that it's not worth the hassle. Using
>unnumbered to customers means you need to have enough address space in
>your loopback so that you don't have two customers with the same IP
>address connected to the same box.
Not worth the hassle? I considered it greater hassle to use /30s. Had to
keep track of all the /30 assignments, carry them in the IGP, etc, etc. I
know many ISPs who have used ip unnumbered for years, and I did too, in my
time. ;-) I'm not clear what is meant by address space in your loopback. A
loopback has only one IP address, the /32 you assign and use for router-id,
iBGP, update-source... For Vinod's and everyone else's benefit the config
looks like:
int loop 0
ip address x.x.x.x
int ser y/y
description customer y
ip unnumbered loop 0
ip route y.y.y.y/mask ser y/y
...and repeat the serial part and static route part as often as you like.
If the customer wants to do link tests, they simply ping the loopback of
the aggregation router. No point to point link to go into the IGP, the
customer route y.y.y.y/mask is in iBGP with the router loopback address as
the next-hop address. (You can do the same thing with next-hop-self in iBGP
with /30s on the point to point links, and block the /30s from appearing in
the IGP. Same result, you just have to tell the registries that you are
consuming /30s for point to point addresses...)
>And IP unnumbered in the core your
>network is a Bad Idea; *very* difficult to troubleshoot problems if
>traceroute doesn't tell you anything about which physical link you
>cross.
Agreed! While it does work, it's a nightmare to troubleshoot. Been there,
tried it too. I generally recommend carrying the network addresses of all
WAN/LAN links which have an IGP running over them in the IGP, otherwise it
really does get unmanageable.
philip
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