[quagga-users 13879] Re: subnet /31

Andrzej Dopierała undefine at aramin.net
Mon Jan 5 20:43:54 GMT 2015


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W dniu 05.01.2015 o 17:32, Greg Troxel pisze:
>
> Sébastien 65 <sebastien-65 at live.fr> writes:
>
>> 10.1.1.1/31 and 10.1.1.2/31 for interconnect two hosts.
>
> Those addresses are not in the same prefix.
>
> Generally a /31 is trouble because in a prefix the 0 address is not used
> and the all-1s address is the broadcast address.  So that doesn't leave
> any for hosts :-)
as point2point - /31 prefix works fine - even with quagga and bgp.

[root at XXX ~]# ip a s dev eth0.Y
17: eth0.Y at eth0: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
group default
    link/ether 00:25:zz:zz:zz:zz brd ff:ff:ff:ff:ff:ff
    inet 185.z.z.9/31 scope global eth0.Y
       valid_lft forever preferred_lft forever
    inet6 fe80::225:90ff:xxx:xxx/64 scope link
       valid_lft forever preferred_lft forever
[root at XXX ~]# ping 185.z.z.8
PING 185.z.z.8 (185.z.z.8) 56(84) bytes of data.
64 bytes from 185.z.z.8: icmp_seq=1 ttl=64 time=8.50 ms
64 bytes from 185.z.z.8: icmp_seq=2 ttl=64 time=8.40 ms
^C
- --- 185.z.z.8 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 8.405/8.454/8.503/0.049 ms

If prefix /31 is used - there is just no place for "directed broadcast".
This is specified in RFC3021.





- -- 
Regards,
Andrzej 'The Undefined' Dopierała
http://andrzej.dopierala.name/
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