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Title: IPSEC OSPF opnsense 26.7
Post by: Denniz on July 16, 2026, 11:43:02 AM

Hi!

I upgraded to 26.7 and now OSPF in IPSEC dosent work for me.

I have an IPSEC VTI tunnel to a cisco router, the cisco router initiates the connection and the tunnel itself works. Since the update, OSPF just stops working some minutes and then comes back to life.

I see this in the OSPF logs - *** sendmsg in ospf_write failed to 224.0.0.5, id 0, off 0, len 120, interface ipsec10, mtu 1400: Network is unreachable

The network type is Point-to-multipoint and eveything worked before the upgrade, any clues?

Title: Re: IPSEC OSPF opnsense 26.7
Post by: nero355 on July 16, 2026, 02:55:27 PM

Quote from: Denniz on July 16, 2026, 11:43:02 AMany clues?

I would say your MTU needs to be a bit lower, but I am not exactly the expert on the subject!

My expectation would be to see something like 1340 or so...

/EDIT :
Hmm... there seems to be something going on with IPSEC in general : https://forum.opnsense.org/index.php?topic=52415.0

Title: Re: IPSEC OSPF opnsense 26.7
Post by: Denniz on July 16, 2026, 05:32:04 PM

I tried to lower the mtu but it didnt help, hoping someone has a solution for this soon :/

Title: Re: IPSEC OSPF opnsense 26.7
Post by: Denniz on July 16, 2026, 05:37:57 PM

Log from FRR

2026-07-16T17:35:38
Error
ospfd
*** sendmsg in ospf_write failed to 224.0.0.5, id 0, off 0, len 120, interface ipsec10, mtu 1400: Network is unreachable
2026-07-16T17:35:38
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Exchange -> Full (ExchangeDone)
2026-07-16T17:35:38
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Full -> Deleted (InactivityTimer)
2026-07-16T17:34:58
Error
ospfd
*** sendmsg in ospf_write failed to 224.0.0.5, id 0, off 0, len 120, interface ipsec10, mtu 1400: Network is unreachable
2026-07-16T17:34:58
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Exchange -> Full (ExchangeDone)
2026-07-16T17:34:58
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Full -> Deleted (InactivityTimer)
2026-07-16T17:34:18
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Exchange -> Full (ExchangeDone)
2026-07-16T17:34:18
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Full -> Deleted (InactivityTimer)
2026-07-16T17:33:38
Error
ospfd
*** sendmsg in ospf_write failed to 224.0.0.5, id 0, off 0, len 120, interface ipsec10, mtu 1400: Network is unreachable
2026-07-16T17:33:38
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Exchange -> Full (ExchangeDone)
2026-07-16T17:33:38
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Full -> Deleted (InactivityTimer)
2026-07-16T17:32:58
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Exchange -> Full (ExchangeDone)
2026-07-16T17:32:58
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Full -> Deleted (InactivityTimer)
2026-07-16T17:32:28
Error
ospfd
*** sendmsg in ospf_write failed to 224.0.0.5, id 0, off 0, len 120, interface ipsec10, mtu 1400: Network is unreachable
2026-07-16T17:32:28
Notice
ospfd
AdjChg: Nbr 172.28.0.29, NbrIP 172.28.0.21 (default) on ipsec10:172.28.0.20: Loading -> Full (LoadingDone)

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English Forums => 26.7 Series => Topic started by: Denniz on July 16, 2026, 11:43:02 AM