OSPFv3 Issues and Suggestions

eprom · Thu Aug 12, 2010 5:05 pm

Hello,
I'm currently evaluating a RB411 as a base station SBC for our PtMP wireless network. I've already configured and implemented OSPFv2 and so far, all went fine. However, I decided to configure OSPFv3 as well, in order to have a similar routing configuration with IPv4. During my tests, I encountered a few "glitches" and an important issue with LSAs.

The routerboard is connected to a Juniper firewall running JUNOS, and the following has an uplink to a Cisco router. I followed the procedure for which I am accustomed, to configure the RB411, like configuring a loopback address, configuring the areas and so on.. I first came to the conclusion that a few important features are missing (as for ospfv2), like the reference-bandwidth command (that would be pretty useful for a higher-end board). Then, once OSPFv3 was configured, I discovered that a prefix was missing from the routing table, despite the fact the corresponding LSA was present in the ospf's database. Here's the output of the database:

[eprom@WAP2] > /routing ospf-v3 lsa print detail 
 instance=default area=area2 type=link id=0.0.0.1 originator=10.2.3.1 
   sequence-number=0x8000000A age=2297 checksum=0xF0C0 options="V6|E|R|DC" 
   body=
     on=vlan500
     priority=128
     local-address=fe80::b2c6:9a01:f473:8482
         prefix=2001:620:2010:200::/64 options=00000000 

 instance=default area=area2 type=link id=0.0.0.9 originator=10.2.3.2 
   sequence-number=0x80000009 age=996 checksum=0xA9D7 options="V6|E|R" 
   body=
     on=vlan500
     priority=1
     local-address=fe80::20c:42ff:fe4d:842b
         prefix=2001:620:2010:200::/64 options=00000000 

 instance=default area=area2 type=router id=0.0.0.0 originator=10.2.3.1 
   sequence-number=0x8000000C age=1226 checksum=0xE7E9 options="V6|E|R|DC" 
   body=
     flags=
         link-type=Transit iface-id=1 neighbor-iface-id=1 neighbor-routerId=10>

 instance=default area=area2 type=router id=0.0.0.0 originator=10.2.3.2 
   sequence-number=0x80000008 age=996 checksum=0xF3EF options="V6|E|R" 
   body=
     flags=
         link-type=Transit iface-id=1 neighbor-iface-id=1 neighbor-routerId=10>

 instance=default area=area2 type=network id=0.0.0.1 originator=10.2.3.1 
   sequence-number=0x80000007 age=876 checksum=0x9A36 options="V6|E|R|DC" 
   body=
         routerId=10.2.3.1
         routerId=10.2.3.2

 instance=default area=area2 type=intra-area-prefix id=0.0.0.1 
   originator=10.2.3.1 sequence-number=0x8000000F age=148 checksum=0x5E56 
   options="" body=
     referenced-LS-type=Router LSA
     referenced-LS-ID=0
         prefix=2001:620:2010:2fe::c/126 options=00000000 
         prefix=2001:620:2010:203::1/128 options=01000000  (LA)

 instance=default area=area2 type=intra-area-prefix id=0.0.0.2 
   originator=10.2.3.1 sequence-number=0x80000007 age=526 checksum=0x56CC 
   options="" body=
     referenced-LS-type=Network LSA
     referenced-LS-ID=1
         prefix=2001:620:2010:200::/64 options=00000000

The routing table is missing the advertised "2001:620:2010:203::1/128" prefix, as shown below:

[eprom@WAP2] >  /ipv6 route print 
Flags: X - disabled, A - active, D - dynamic, 
C - connect, S - static, r - rip, o - ospf, b - bgp, U - unreachable 
 #      DST-ADDRESS              GATEWAY                  DISTANCE
 0 ADC  2001:620:2010:200::/64   vlan500                  0       
 1 ADC  2001:620:2010:202::/64   vlan502                  0       
 2 ADC  2001:620:2010:203::2/128 lo0                      0       
 3 ADo  2001:620:2010:2fe::c/126 fe80::b2c6:9a01:f473:... 110

I also encountered another issue, where the router fails to install LSA originated from the Cisco router. Here's an extract of the logs:

15:49:35 route,ospf,warning LSA installation failed 
15:49:35 route,ospf,warning     header=Summary Network LSA id=0.0.0.78 originator=10.2.255.1 seqnum=0x800005b6 
15:49:35 route,ospf,warning LSA installation failed 
15:49:35 route,ospf,warning     header=Summary Network LSA id=0.0.0.79 originator=10.2.255.1 seqnum=0x800005b6

Any pointers or suggestions regarding the issue?

xxiii · Thu Sep 09, 2010 1:14 am

I would suggest avoiding /128 (and the /126) and using /64 instead, even for loopbacks.

ipv6 isn't really designed or meant for the lower /64 to be subnetted any further.

Note however if you do use /64's cisco has an opposite problem (I presume because of backwards compatibility with their implementation being older than ipv6 being finalized) and you may have to add "ipv6 ospf network point-to-point" to your loopback(s) to get the cisco to advertise them correctly. I'm not sure about Juniper.

Reasoning (also see ipv6 related RFCs)

Depending on your allocation, you've got either 65536 /64's or 4 billion /64's if your upstream is allocating them correctly (or possibly only 1 if they only allocated you a single network; if your "upstream" is part of the same AS though you could have something funky). And each of those /64s can handle trillions of hosts.

upstreams are generally supposed to be allocating either /64 or /48 to downstream customers, depending on if the downstream indicated they needed to be able to subnet or not. (or put another way, generally speaking, if you're an individual you get a /64, if you're a business or a power-user you get a /48 and if you're an ISP or really large business that can justify more than 65000 subnets (counting loopbacks as subnets) you get a /32.

In short, ipv6 was designed (amongst other things) to get rid of the notion of scarce resource allocation, partially to simplify the work routers have to do to deal with subnets.

Also, I note that reference-bandwidth is really a convenience feature (which would be nice to have, as long as it can be overridden), and doesn't really have anything to do with the running of OSPF, only easing configuration of it. reference-bandwidth in conjuction with interfaces that could auto-calculate their own cost periodically (such as wireless links) would be nice to have though. Preferably with user-specified intervals. (cost recalculations could cause momentary routing loops until the new cost is fully propogated).

marcof · Thu Dec 22, 2011 6:09 pm

Hi,

Did you solve your problem? I think we are talking about the same problem: http://forum.mikrotik.com/viewtopic.php?f=14&t=57817

thanks,
marco

OSPFv3 Issues and Suggestions

OSPFv3 Issues and Suggestions

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