[Xorp-users] [OSPFv2] BUG: ICMP error message ( Time to Live exceeded )

[Bruce M Simpson]

Hi,

This sounds like a real bug, thanks for finding this.

Can you please file a Bugzilla report at http://bugzilla.xorp.org/ to 
make sure the problem is tracked?

karnik wrote:
>
> BUG:  Virtual Adjacency is not getting established between routers 
> because ICMP error message ( Time to Live exceeded ) is generated.
> Because :  Xorp sets TTL field = 1 seconds in unicast Hello packets 
> thats why ICMP message ( Time to Live exceeded ) is getting generated 
> while establishing adjacency with adjacent router.

I took a look at what Quagga does; it checks if the outgoing packet is 
leaving an OSPF virtual-link interface, and if so, increases the TTL of 
the encapsulating IP header to 100.

Normally the FEA will default to a TTL of 1 if the 
IPTOS_PREC_INTERNETCONTROL bit is set for the TOS field of the outgoing 
packet, and 64 in other cases.

To verify a possible solution could you do the following:

In file ospf/xrl_io.cc, try changing the following line in the member 
function XrlIO<IPv4>::send(), recompile, and reinstall:
        true,        // ip_internet_control
to read:
        false,        // ip_internet_control

This should force the FEA to use an outgoing TTL of 64 for OSPF traffic, 
if you could verify this with Wireshark too that would be very useful.

Let me know if this resolves the issue. If you could copy this 
information in the bug report that would be great.

Thanks.
BMS