From: Darek Kuzma (darekk@xxxxxxxxxxxxx)
Date: Fri Jul 19 2002 - 15:14:37 GMT-3
Timothy,
And after doing some thinking I believe that tag 1 for 0/0 comes from OSPF
process number.
Are you using 1 ??
Change it to sth and see what happens.
I think it is understandable that OSPF will mark the route for 0/0 because rout
e
is originated there.
We don't want BGP to advertise 0/0 to the backbone anyway on the other end of
IGP domain (of cause in scenario from Doyle)
Let me know how it went with this tag for 0/0.
Thanks,
Darek
Darek Kuzma wrote:
> Timothy,
> As far as tag for redistributed routes into OSPF it is normal!
> OSPF (and EIGRP (checked) and possibly RIP v2 (didn't check) ) automatically
> uses tag to convey path info through IGP domain.
> In other direction it is not automatic (you need to use route-map with set
> as-path tag)
> I don't know why 0/0 got tag=1. But as far as this is OSPF originated route
> I don't think it is related to the issue described above.
> For more on BGP->OSPF redistribution and use of tags check Doyle volume II
> Thanks,
> Darek
>
> Timothy Ouellette wrote:
>
> > Having another wonderfull night listening to the hum of 10 routers.
> > Here's the deal.
> >
> > router5 ----ebgp--- router3 ----- ospf area 0 ----- r1
> >
> > Router 5 is generating a couple of external networks via the loopback.
> > Namely 172.16.0.0/24, 10.0.0.0/24, 192.168.1.0/24, 69.69.0.0/16, and is
> > also sending in a 0.0.0.0/0 default.
> >
> > On r3, i'm also using a "default-information originate" in order for the
> > ospf speaks behind r1 to get the default. Everything was running fine
> > and I started filtering with OSPF tags.
> >
> > The one thing that I noticed on r1 (see below) is that the 0.0.0.0/0 had
> > already had a tag of "1" so when I started filtering things broke
> > because I assumed that it would have a tag of 0 (like all the other ospf
> > routes prior to modification/redistro)
> >
> > The next odd thing was that the routes that r3 was receving from BGP
> > were getting redistributed into OSPF (i know, i know, bad design) but
> > the weird part is that on r1 they were showing with a tag as 11 (which
> > is the as that r5 is in)
> >
> > Below is a "sh ip ospf d" on r1. Does this look normal? All of the ebgp
> > learned routes sent to r3 from r5 have an ospf tag of 11?
> >
> > r1#sh ip ospf d
> >
> > OSPF Router with ID (141.108.255.5) (Process ID 1)
> >
> > Router Link States (Area 0)
> >
> > Link ID ADV Router Age Seq# Checksum Link
> > count
> > 141.108.3.1 141.108.3.1 1247 0x80000003 0x747B 2
> > 141.108.4.1 141.108.4.1 607 0x80000005 0xF601 1
> > 141.108.255.5 141.108.255.5 1284 0x80000003 0x9888 3
> >
> > Net Link States (Area 0)
> >
> > Link ID ADV Router Age Seq# Checksum
> > 141.108.255.1 141.108.255.5 1284 0x80000002 0xA1A2
> > 141.108.255.5 141.108.255.5 1284 0x80000002 0x6CD4
> >
> > Summary Net Link States (Area 0)
> >
> > Link ID ADV Router Age Seq# Checksum
> > 141.108.4.0 141.108.4.1 1435 0x80000002 0x4607
> >
> > Type-5 AS External Link States
> >
> > Link ID ADV Router Age Seq# Checksum Tag
> > 0.0.0.0 141.108.4.1 425 0x80000001 0xBBF7 1
> > 10.10.10.0 141.108.4.1 581 0x80000001 0x784 11
> > 16.16.16.0 141.108.255.5 1532 0x80000002 0xB1CB 0
> > 69.69.0.0 141.108.4.1 582 0x80000001 0xAC72 11
> > 141.108.1.0 141.108.255.5 1532 0x80000002 0x1A8B 0
> > 141.108.2.0 141.108.255.5 1532 0x80000002 0xAA04 0
> > 141.108.3.0 141.108.255.5 1285 0x80000002 0x9F0E 0
> > 141.108.4.0 141.108.255.5 1285 0x80000002 0x9418 0
> > 141.108.255.0 141.108.255.5 1532 0x80000002 0xC0EF 0
> > 150.150.0.0 141.108.255.5 1532 0x80000002 0xB5BD 0
> > 172.16.1.0 141.108.4.1 582 0x80000001 0xDF0C 11
> > 192.168.1.0 141.108.4.1 582 0x80000001 0xB38B 11
> > r1#
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