[Xorp-users] Questions about Xorp.

[Bruce Simpson]

Welcome.

David Balnaves wrote:
> Hi Xorp Users,
>
> I've just discovered xorp after trying bird and quagga.
>
> I really like quagga but it seems that there were some bugs I couldn't 
> figure a way around and as such I have decided to look into xorp.  There was 
> also a clear lack of support for IGMP & PIM under these routing daemons 
> (while this is not the place, please correct me if I'm wrong!).
>   

That's correct, XORP is the only cohesive multicast routing story in 
open source at the moment.
PIM-SM can have significant complexity, and needs to be low latency, 
which is one reason that a C++ implementation of that protocol is justified.

> So far the XORP work seems really impressive, but I have a few things I 
> would like to clarify:
>
> * Is there any prerequisite configuration needed on the router before XORP 
> is started (including IPv6)?  For example, should I need to configure 
> anything under the debian network scheme of /etc/network/interfaces?
>   

You shouldn't need to configure this further than ensuring essential 
network drivers are loaded -- the XORP configuration file should be able 
to take care of it, unless you have a compelling reason to do otherwise 
(i.e. configure up management interface port on boot -- and use 
default-system-config directive for that interface in the XORP config).

> * To my understanding Xorp doesn't appear to support IPv6 router 
> advertisements for auto address configuration, is this correct?  Is there 
> plans to implement this functionality?
>   

That's correct. People have requested this feature before. I don't 
believe there is a Bugzilla entry for this feature request.
Adding it would require code modification.

> * I'm using OSPFv3 for IPv6.  I see some IPv6 interfaces on my Xorp router 
> that return "destination host unreachable".  When I query the route I see:
> 2002:XXXX:XXXX:4::1 via 2002:XXXX:XXXX:4::1 dev eth1  src 2002:XXXX:XXXX::2 
> metric 0
>     cache  mtu 1500 advmss 1440 hoplimit 4294967295
>
> I also see that the the interface has "scope global tenative", what does 
> this mean?  Is there a way to resolve this issue?
>   

A tentative address in IPv6 is usually one for which the Duplicate 
Address Detection (DAD) mechanism may have failed. Are you using 
stateless address autoconfiguration on these interfaces?

> 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state 
> UNKNOWN qlen 1000
>     link/ether 00:40:48:b1:23:36 brd ff:ff:ff:ff:ff:ff
>     inet 192.168.4.1/24 brd 192.168.4.255 scope global eth1
>     inet6 2002:XXXX:XXXX:4::1/64 scope global tentative
>        valid_lft forever preferred_lft forever
>     inet6 fe80::240:48ff:feb1:2336/64 scope link tentative
>        valid_lft forever preferred_lft forever
>
> Also, I understand that in OSPFv3 the link local is used for next hop 
> routing.  Is there a reason why you need to declared the link local address 
> (ie: fe80:) on the interface under OSPFv3 protocol?  Why isn't this 
> inherited from the interface?
>   

Yes, in OSPFv3 the link-local addresses normally need to be used, 
although I believe that was only a requirement for XORP release 1.4.

The user manual says:
%%%
OSPFv3 does not require any addresses to be configured in which case it 
will advertise all global
addresses configured on the interface/vif. If any addresses are 
configured in OSPFv3 then only those
addresses will be advertised. If it is required that no addresses should 
be advertised then configuring
an address and disabling it, will stop any global addresses being 
advertised.
%%%

Are you trying to configure only specific interfaces for OSPFv3 use? If 
so, it sounds like perhaps there should be a configuration switch to 
request the link-local address be bound for OSPFv3 without actually 
specifying it, for convenience.
> * Xorp seems to do mostly everything from within the CLI.  Is there syntax 
> to declare if I an address should be gained from DHCP, or RA in the case of 
> IPv6?
>   

No, there is currently no DHCP client support in XORP itself.
Normally we rely on the host platform's mechanisms for doing this.

This could potentially be added at a later date, user contributions are 
welcome -- discussions are in progress about how to improve the software 
component model in XORP to facilitate such additions.

> Either way, I think XORP is awesome.  I'd love to get the chance to use this 
> in a production environment!
>
>   

Thanks!
BMS