[Xorp-users] Questions on OSPF
Atanu Ghosh
atanu at ICSI.Berkeley.EDU
Thu Sep 13 12:18:42 PDT 2007
>>>>> "kristian" == kristian <kristian at spritelink.net> writes:
kristian> On Thu, 13 Sep 2007 11:51:32 -0700, Atanu Ghosh
kristian> <atanu at icsi.berkeley.edu> wrote:
>>>>>>> "Kristian" == Kristian Larsson <kristian at spritelink.net>
>>>>>>> writes:
>>
Kristian> Hansi wrote:
>> >> Hello All,
>> >>
>> >> I'm currently learning how to configure OSPFv2 on two XORP >>
>> machines just to establish adjacency with one another. In a p2p
>> >> link type, is it still necessary to explicitly set the
>> 'neighbor' >> parameter of each machine before adjacency is
>> established? >> Furthermore, would it be possible to set the
>> router-id to its >> loopback address? instead of say.. the ip
>> address of the >> interface on which ospf will be used?
>>
Kristian> The neighbor command is only useful if you are using a
Kristian> medium on which the routers cannot broadcast and thus
Kristian> cannot discover each other. If you're using ethernet
Kristian> (which I presume from your NIC names) you do not have to
Kristian> use the neighbor statements. I would advice configuring
Kristian> the interfaces as link-type p2p as this avoids DR election
Kristian> and unnecessary CPU load.
>> I am fairly sure that it is necessary to use the neighbour
>> statements.
kristian> Are you serious? I haven't used the XORP code in quite
kristian> some time now.. but at least I thought XORP implemented
kristian> the OSPF standard. AFAIK, that includes being able to
kristian> discover neighbors and turn up adjacencies to them. Is
kristian> this not the case? Observe that he is running an Ethernet
kristian> point-to-point link, ie, it is not a non-broadcast medium.
kristian> Or are you saying that you can't do link-type p2p without
kristian> configuring neighbours ?
If the link-type is set to "broadcast" then the neighbours will be
correctly discovered. If the link-type is set to "p2p" (Point-to-point)
or "p2m" (Point-to-multipoint) then it is necessary to configure the
neighbours. It has been argued that it should not be necessary to
configure the neighbours if the routers are connected via a true
Point-to-point link, but unfortunately even in this case it is necessary
to configure the neighbour.
Atanu.
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