Cisco Systems dynamic vpn keep alive

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Subject Author Date
dynamic vpn keep alive sali 06-14-09
Posted by sali on June 14, 2009, 5:45 pm
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situation:
i have cisco 1841 [headq] on static address and cisco 876 [branch office] on
dynamic adsl address
it is configured an ipsec vpn tunnel between them so both locations are part
of corporate network [wan]
when the tunnel is up, i may reach headq from branch, and branch from headq
as well, this is ok

problem:
but, when 876 adsl address changes [regularly], obviously tunnel is going
down, and i need incoming call [f.e. ping] from branch office to static
headq [well known ip] to re-establish the tunnel. it is then ok for next
period

current solution:
at branch office, i have one dedicated workstation allways powered-on that
serves as ping generator, to keep tunnel to headq on. i was not trying any
solution based on dyndns or similar.

question:
is it possible to configure cisco 876 router to periodicaly issue ping [or
something similar] on frequent basis [few minutes] to force tunnel
re-establish after adsl address change


any suggestions?

thnx!



Posted by bod43 on June 14, 2009, 6:35 pm
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> situation:
> i have cisco 1841 [headq] on static address and cisco 876 [branch office] on
> dynamic adsl address
> it is configured an ipsec vpn tunnel between them so both locations are part
> of corporate network [wan]
> when the tunnel is up, i may reach headq from branch, and branch from headq
> as well, this is ok
>
> problem:
> but, when 876 adsl address changes [regularly], obviously tunnel is going
> down, and i need incoming call [f.e. ping] from branch office to static
> headq [well known ip] to re-establish the tunnel. it is then ok for next
> period
>
> current solution:
> at branch office, i have one dedicated workstation allways powered-on that
> serves as ping generator, to keep tunnel to headq on. i was not trying any
> solution based on dyndns or similar.
>
> question:
> is it possible to configure cisco 876 router to periodicaly issue ping [or
> something similar] on frequent basis [few minutes] to force tunnel
> re-establish after adsl address change
>
> any suggestions?
>
> thnx!

track 1 rtr 101 reachability
delay down 20 up 20
ip sla 101
icmp-echo 10.0.0.1
timeout 1000
ip sla schedule 101 life forever start-time now

Or
NTP can be used.

In both cases you are likely to require to set the
source address for the traffic since you have a vpn.

Posted by sali on July 20, 2009, 4:12 pm
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grupi:6d9aeb0f-ba4b-40e6-85c4-0435f8946dec@c18g2000prh.googlegroups.com...

>> is it possible to configure cisco 876 router to periodicaly issue ping
>> [or
>> something similar] on frequent basis [few minutes] to force tunnel
>> re-establish after adsl address change
>
> track 1 rtr 101 reachability
> delay down 20 up 20
> ip sla 101
> icmp-echo 10.0.0.1
> timeout 1000
> ip sla schedule 101 life forever start-time now

just to say that my netw admin has done something upon your suggestion, and
since that, vpn-over-adsl is working well for few weeks.

thnx again!



Posted by bod43 on July 21, 2009, 12:51 am
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> grupi:6d9aeb0f-ba4b-40e6-85c4-0435f8946...@c18g2000prh.googlegroups.com...
>
> >> is it possible to configure cisco 876 router to periodicaly issue ping
> >> [or
> >> something similar] on frequent basis [few minutes] to force tunnel
> >> re-establish after adsl address change
>
> > track 1 rtr 101 reachability
> > delay down 20 up 20
> > ip sla 101
> > icmp-echo 10.0.0.1
> > timeout 1000
> > ip sla schedule 101 life forever start-time now
>
> just to say that my netw admin has done something upon your suggestion, and
> since that, vpn-over-adsl is working well for few weeks.
>
> thnx again!

That's good, always nice to hear that I am
not completely clueless.

Saying that, I have just faked up NTP in the past:-)
The SLA stuff is not that easy to follow.

Good luck.

Posted by sali on July 22, 2009, 3:04 am
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grupi:edfdeb0f-7a67-4f21-ab3a-59211935edbf@w41g2000yqb.googlegroups.com...
>> grupi:6d9aeb0f-ba4b-40e6-85c4-0435f8946...@c18g2000prh.googlegroups.com...
>>
>> just to say that my netw admin has done something upon your suggestion,
>> and
>> since that, vpn-over-adsl is working well for few weeks.
>
> That's good, always nice to hear that I am
> not completely clueless.

this cisco-876 is a funny device, i have few of them, and having other
problems with them too

there is a branch office with few employees, cisco-876 adsl [but in this
case, there is static ip, if it counts], and one of computers is not able to
send mail. cisco passes just the first few hundreds of bytes over port 25
[smtp] and then stops, so, from that very computer, it is possible to send
only very short mails. after reseting the cisco 876-router, it sends mail
correctly for next few days.
and again, this happens only on *one* of computers, all other whole time
sends mails [no matter how long they are] without any problem.
i have noticed this problem in two branch offices, with two different
cisco-876
i have checked this problem not just with mail client [you really don't know
what does mail client is doing], but also with telnet, over port 25. and
after few lines sent, the traffic realy blocks

my assumptions were that cisco-876 builds some internal tables based on
computer's nic mac, and somehow, maybe because of some traffic overload,
this respective nic mac appears stucked, and its traffic over port 25
blocked

have you maybe any clue what can be done to resolve [or further investigate]
this problem?

thnx!



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