As-path-prepend does not work

General questions
1

Hello,

I have an issue where my router is not announcing routes to eBGP neighbor routes with prepended AS (5 times)
Please have a look at the config and let me know what I am doing wrong. I am new to VyOS.

When I configured the router as below, I was sending to the neighbour full internet routing table! I altered the configuration to remove the as-path-prepend statement everything work as it should - just sending our routes. However because this is not our main line, but backup line I need to change the configuration back and prepend our routes with our AS number.

Thank you for your help.

prefix-list CSG-PREFIXES {
    description CSG_announced_prefix_list
    rule 10 {
        action permit
        le 24
        prefix 185.23.52.0/22
    }
    rule 11 {
        action permit
        le 24
        prefix 46.17.208.0/21
    }
    rule 12 {
        action permit
        le 24
        prefix 185.33.192.0/23
    }
    rule 13 {
        action permit
        le 24
        prefix 185.77.20.0/22
    }
    rule 14 {
        action permit
        le 24
        prefix 185.79.108.0/22
    }
    rule 15 {
        action permit
        le 24
        prefix 185.98.108.0/22
    }
    rule 16 {
        action permit
        le 24
        prefix 185.80.12.0/22
    }
    rule 20 {
        action permit
        prefix 193.111.33.0/24
    }
    rule 30 {
        action permit
        le 24
        prefix 193.33.116.0/23
    }
    rule 40 {
        action permit
        prefix 194.147.241.0/24
    }
    rule 41 {
        action permit
        prefix 194.147.244.0/24
    }
    rule 42 {
        action permit
        prefix 194.147.255.0/24
    }
    rule 43 {
        action permit
        prefix 194.149.89.0/24
    }
}
prefix-list DIDLOGIC-PREFIXES {
    description DIDLOGIC_announced_prefix_list
    rule 10 {
        action permit
        prefix 185.118.60.0/24
    }
}
   route-map OUT-HNS-v4 {
    description EXPORT_ROUTES_TO_HNS
    rule 10 {
        action permit
        match {
            ip {
                address {
                    prefix-list CSG-PREFIXES
                }
            }
        }
    }
    rule 12 {
        action permit
        match {
            ip {
                address {
                    prefix-list DIDLOGIC-PREFIXES
                }
            }
        }
    }
    rule 90 {
        action permit
        set {
            as-path-prepend "59455 59455 59455 59455 59455"
        }
    }
    rule 100 {
        action deny
    }
}

protocols {
bgp 59455 {
neighbor 87.237.67.6 {
description HNS_Backup_Transit
ebgp-multihop 6
nexthop-self
remote-as 39537
route-map {
export OUT-HNS-v4
import IN-HNS-v4
}
soft-reconfiguration {
inbound
}
timers {
holdtime 90
keepalive 30
}
}
}
}

2

If I understand correctly you need to export only some prefixes that defined in prefix-list (with prepend) to your eBPG neighbor and don’t send full-view?

3

Yes that is correct.

4

Delete rule 90 from policy-map. So you export specific prefixes without prepending and fullview table with prepending.

Change your policy route-map like this.

set policy route-map OUT-HNS-v4 rule 10 action 'permit'
set policy route-map OUT-HNS-v4 rule 10 match ip address prefix-list 'CSG-PREFIXES'
set policy route-map OUT-HNS-v4 rule 10 set as-path-prepend '59455 59455 59455 59455 59455'
5

I will try to implement the config out of hours and let you know.

Thanks

6

Thank you. It worked perfectly.

7

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