08-12-2008 02:59 PM - edited 03-03-2019 11:07 PM
Hi Guys,
What does the following prefix-list mean. Does it mean permit a default route to the neighbour (i mean send a default to the neighbour)
ip prefix-list BGP-to-Telstra seq 10 permit 0.0.0.0/0
And also what does the following mean. specially the ie 32:
ip prefix-list BGP-from-Telstra seq 5 permit 10.0.0.0/8 le 32
Tks
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08-12-2008 04:38 PM
The first line matches (in theory) only the default route. Although it could also match any route with a 0 subnet mask, but in practice this doesn't come up.
ip prefix-list BGP-from-Telstra seq 5 permit 10.0.0.0/8 le 32
The second line matches any route in 10.0.0/8. The le 32 means less than or equal to 32 bit subnet mask. In practice this will match every subnet in 10.0.0.0/8 no matter how it is subnetted.
This looks like a pretty standard enterprise MPLS access list to me, it says:
Allow the default route
Allow the enterprise routes in the 10.0.0.0/8 network.
Regards,
R.
08-12-2008 04:38 PM
The first line matches (in theory) only the default route. Although it could also match any route with a 0 subnet mask, but in practice this doesn't come up.
ip prefix-list BGP-from-Telstra seq 5 permit 10.0.0.0/8 le 32
The second line matches any route in 10.0.0/8. The le 32 means less than or equal to 32 bit subnet mask. In practice this will match every subnet in 10.0.0.0/8 no matter how it is subnetted.
This looks like a pretty standard enterprise MPLS access list to me, it says:
Allow the default route
Allow the enterprise routes in the 10.0.0.0/8 network.
Regards,
R.
08-12-2008 07:59 PM
so what is matched by
ip prefix-list BGP-from-Telstra seq 5 permit 0.0.0.0/32
and
ip prefix-list BGP-from-Telstra seq 5 permit 0.0.0.0/0 le 32
08-13-2008 05:11 AM
The first one (/32) probably doesn't match anything. Have you ever seen the route "0.0.0.0" with subnet mask "255.255.255.255"? If you do, it's probably being spoofed.
The second one:
ip prefix-list BGP-from-Telstra seq 5 permit 0.0.0.0/0 le 32
That permits every route of every prefix length.
Regards,
Ryan
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