[j-nsp] BGP "Holdtime", " Active Holdtime" and "Preference" values

[Martin T]

David, Stefan:
I configured "hold-time 20" and BGP session came up with an "Active
Holdtime: 20" as expected. Thank you for explanations!


regards,
martin

2011/8/9 Stefan Fouant <sfouant at shortestpathfirst.net>:
> On 8/9/2011 7:55 AM, Martin T wrote:
>>
>> Hi,
>> in case one has following settings active with it's BGP peer:
>>
>>   Holdtime: 90 Preference: 170
>>   Active Holdtime: 90
>>   Keepalive Interval: 30
>>
>> ..then what do they mean? As I understand, "Holdtime" is the maximum
>> number of seconds allowed to elapse between the time that a BGP system
>> receives successive keepalive or update messages from a peer. So if
>> the holdtime is configured to 90s, the "Holdtime" value under "show
>> bgp neighbor I.I.P.P" doesn't change, does it? How is "Active
>> Holdtime" different from "Holdtime"? And what does this "Preference"
>> mean?
>
> Holdtime is the configured holdtime on the local device, whereas Active
> Holdtime is the negotiated holdtime between the two peers, which should be
> the minimum of the two peers holdtime configuration.
>
> Preference is the value we assign to BGP routes learned from this neighbor,
> which in this case is 170, the default.  Preference is the equivalent of
> Administrative Distance in Cisco, and allows the router to determine which
> route to prefer should the identical route be learned from multiple sources
> (ex: RIP[100] vs. BGP[170]).
>
>> Last but not least- in case of the configuration above, is it possible
>> that the connection between peers is down for example 80 seconds and
>> then comes back up, but as holdtime is set to 90s, the session stays
>> up?
>
> Yes.
>
> Stefan Fouant
> JNCIE-ER, JNCIE-M, JNCIE-SEC, JNCI
> Technical Trainer, Juniper Networks
> http://www.shortestpathfirst.net
> http://www.twitter.com/sfouant
>