Routing

Hello- i was trying to redistribute an default route 0/0 to an EBGP peer. I created an aggregate route 0/0 and the craeted a policy

set policy-options policy-statement adv-default from protocol aggregate

set policy-options policy-statement adv-default from route-filter 0/0 exact

set policy-options policy-statement adv-default then accept

set policy-options policy-statement then reject

and i applied this as export to ebgp neighbor

tthe route exported ok but with a AS Path that was like 100 ASNs deep. It had my local ASN first and then all kinds of other ASN that i have no idea where those came from.

Has anyone seen this before. I'd sure like to get an explanantion of where the other ASNs came from with the above policy

TIA

The aggregate route becomes active as a result of the presence of more specific routes in the routing table. Since the aggregate route in your case is a default route, every route in the routing table is a potential contributor. You can do a "show route protocol aggregate detail/extensive" to see the contributing routes and their attributes. You can use a policy to specify the contributing routes you would like to make the generated route active if you so desire.

ah ok..would a generated route be better in this case to if i want to send a default out to my EBGP peers??

Hi,

It is better to use default route in your routing table

> show route 0.0.0.0

if it is static so in the export policy should be from protocol static and so on. If you don't have default route but just want to advertise default route to your peer instead of your hole subnet range try to configure static route 0.0.0.0/0 and export from protocol static like

# set routing-options static route 0.0.0.0/0 discard

Mohamed Elhariry

JNCIE-M/T # 1059, CCNP & CCIP

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You could set the as-path on the aggregate itself to your own ASN.

Using this:

set routing-options aggregate route 0.0.0.0/0 as-path path 65097

 yields this:

0.0.0.0/0          *[BGP/170] 00:04:27, localpref 100, from 10.12.14.255
                      AS path: 65097 65097 I
                    > to 192.168.254.2 via ge-1/3/9.0

Still not ideal since the ASN is listed twice instead of once, but it at least gets rid of all the other ASNs.  Using the floating static is a better option and would send it exactly as expected, with a single ASN.  If you opt for that method, and set the static discard route to a very high preference so it isn't the active route, make sure you add "advertise-inactive" to the peer.

-Chad

Ah-ha, even bettter.  The aggregator option.

route 0.0.0.0/0 {
    as-path {
        aggregator 65097 10.12.14.255;
    }
}

 yields exactly what is wanted:

0.0.0.0/0          *[BGP/170] 00:00:07, localpref 100, from 10.12.14.255
                      AS path: 65097 I
                    > to 192.168.254.2 via ge-1/3/9.0



cmyers@lab-1> show route 0/0 exact detail  

inet.0: 62 destinations, 63 routes (61 active, 0 holddown, 1 hidden)
0.0.0.0/0 (1 entry, 1 announced)
        *BGP    Preference: 170/-101
                Next hop type: Indirect
                Address: 0x2782448
                Next-hop reference count: 6
                Source: 10.12.14.255
                Next hop type: Router, Next hop index: 578
                Next hop: 192.168.254.2 via ge-1/3/9.0, selected
                Protocol next hop: 10.12.14.255
                Indirect next hop: 28a0000 1048574
                State: <Active Ext>
                Local AS: 65098 Peer AS: 65097
                Age: 1:28       Metric2: 3 
                Task: BGP_65097.10.12.14.255+179
                Announcement bits (2): 0-KRT 3-Resolve tree 1 
                AS path: 65097 I
                Aggregator: 65097 10.12.14.255
                Accepted
                Localpref: 100
                Router ID: 10.12.14.255

Cheers!

-Chad

nice...lots of options..thanks all

If you have a BGP learned default route, this would be sent to your EBGP peers by default, no pun intended. you could export only this default route to them, and modify the AS path to whatever you like with an export policy. If you're learning the full internet routing table, as is likely if you're providing transit services, then I would put a static discad, as previously suggested, with a 254 preference, or a generated policy route, as also was suggested.