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startx001
Beginner

bgp question 7609

If can anyone help

when i issue command "sh ip bgp" it shows

* i 0.0.0.0          a.b.c.d          0     90      0 ASN i

*                      a.b.c.d             0     90      0 ASN i

*>                    a.b.c.d                  100      0ASN i

                          0.0.0.0                                0 i                <<----------------

*   1.0.0.0/24      a.b.c.d                90      0 5483 15169 i

*                    a.b.c.d                   90      0 5483 15169 i

*>                   a.b.c.d                   90      0 8400 15169 i

Refresh Epoch 1

  Local, (default-originate)

    0.0.0.0 from 0.0.0.0 (aa.bb.cc.dd)               <--  aa.bb.cc.dd is  loopback ip on same router

      Origin IGP, localpref 100, external

Can anyone help , why is this .

3 REPLIES 3
mwandu
Beginner

hi,

I think you are orginating a default route (0.0.0.0) within your BGP configuraton. please confirm you have the following command within bgp configuration;

- default-information originate

No i dont have that .

I mean i have , but only to bgp customers .

like :

neighbor aaa.bbb.ccc.ddd default-originate

aaa.bbb.ccc.ddd is ip of customer router

Hello,

even though it appears in the BGP table, it's not going to be a candidate to the RIB table. I have seen in previous IOS versions that, when this command is applied (neighbor x.y.z.x default-originate) the result is that the peer is advertising a default route dynamically regardless if it has a default route in the RIB or not. Also, it does not install a default in the BGP table and it bypasses the BGP filters (Adj-Rib-Out). I have tested in IOS 15.0M and I have got the same results that you have posted. I have tested the behavior of this and it appears to me just a "cosmetic" thing in the router:

R1 is advertising a default route to R2

R1#show ip bgp

BGP table version is 2, local router ID is 10.1.12.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

   0.0.0.0          0.0.0.0                                0 i

However, it does not appear in the RIB:

R1#show ip route 0.0.0.0

% Network not in table

I have installed another default route as a matter of fact that the previous one is not taken into account:

ip route 0.0.0.0 0.0.0.0 Null0

!

Router bgp 1

network 0.0.0.0 route-map TEST

The route-map TEST sets the weight to 0 and Local Preference to 0 to become worse than the other:

route-map TEST permit 10

set local-preference 0

set weight 0

But, as you can see, it is the best as the other one is not eligible:

R1#sh ip bgp 0.0.0.0

BGP routing table entry for 0.0.0.0/0, version 10

Paths: (2 available, best #1, table default)

  Advertised to update-groups:

     1

  Local

    0.0.0.0 from 0.0.0.0 (10.1.12.1)

      Origin IGP, metric 0, localpref 0, valid, sourced, local, best

  Local, (default-originate)

    0.0.0.0 from 0.0.0.0 (10.1.12.1)

      Origin IGP, localpref 100, external

Best Regards,

Jose