From: Ouellette, Tim (tim.ouellette@xxxxxxx)
Date: Tue Jul 23 2002 - 03:27:21 GMT-3
Hmm, I saw the exact same thing the other night. The BGP into OSPF/EIGRP
thing is normal. my "default-information originate" had a tag of "1" which
was the ospf process id. Check out the email below....
-----Original Message-----
From: Timothy Ouellette [mailto:timoue@cogeco.ca]
Sent: Friday, July 19, 2002 5:34 AM
To: cisco@groupstudy.com
Subject: ebgp routes tagged when sent into OSPF? Weird Issue? [7:49226]
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#
-----Original Message-----
From: Michael Snyder [mailto:msnyder@ldd.net]
Sent: Tuesday, July 23, 2002 12:07 AM
To: ccielab@groupstudy.com
Subject: Volunteer Tagging
I use tags a lot with the redistributions I do. In fact the only place
I don't use them is incoming rip and igrp routes. Anytime I have routes
coming out of rip or igrp I use distribution lists to the same effect.
I don't know why, but having a rip or igrp route donors seems to really
mess up tagging operations, even with protocols that support tagging
like eigrp or ospf.
Anyway, getting back to my question.
I noticed that some protocol operations product tags. When BGP is the
donor, the receiving protocols seem to have tags matching the AS of the
BGP.
I just saw another example tonight. When I did a default-information
originate in ospf, the resulting external route got tagged equal to '1',
which seems is the same as the process ID.
router ospf 1
router-id 0.0.0.2
log-adjacency-changes
redistribute static
default-information originate metric 20 metric-type 1
OSPF Router with ID (0.0.0.2) (Process ID 1)
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 0.0.0.2 1144 0x80000004 0x64B6 1
My question is, what's up with this volunteer tagging? Are there any
hard rules on this behavior, or is it a special case by special case
basis?
Any tricks to use this behavior to our advantage, any pitfalls to watch
out for?
Thanks in Advance,
Michael
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:40 GMT-3