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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