Comments on ipSpace.net: Loop-Free Alternate: OSPF meets EIGRP

ISR routers support MPLS, 6500's and Nexus su...

2012-01-31T05:35:30.206+01:00

ISR routers support MPLS, 6500's and Nexus support MPLS? What doesn't support it these days? Closet level switches?

In other vendors, Juniper and other support MPLS as well. I think the adoption doesn't have to do with gear as much as it does with education.

Or other "sane" networking operating sys...

2012-01-31T05:33:44.966+01:00

Or other "sane" networking operating systems where archaic timers don't exist. (i.e: Junos). Anyone know the timers on NX-OS?

Nice, except it morse code compared to your articl...

2012-01-27T22:09:51.157+01:00

Nice, except it morse code compared to your articles :)

Strictly speaking, if the links were equal cost, t...

2012-01-27T16:01:05.320+01:00

Strictly speaking, if the links were equal cost, then A would have no feasible successor to X via B if it lost the A-C link. The EIGRP feasibility condition is a strict one, and the cost for B-X via C must be less than A-X via C for the condition to be met.

In practice when testing I see much quicker failover than OSPF dead time expiry. I reckon the link failure is detected in hardware, RIB, FIB entries are removed and this potentially forces OSPF to recalculate a path?

1. For default values on IOS yes, there will be a ...

2012-01-27T11:30:03.971+01:00

1. For default values on IOS yes, there will be a difference but not on IOS XR where timers are tuned by default.

But my comment was for IPLFA vs. EIGRP. :)

#1 - There should be no difference if you fine-tun...

2012-01-27T06:59:08.375+01:00

#1 - There should be no difference if you fine-tune the OSPF/IS-IS timers. With the default values, there will be 5+ second difference.

#3 - Good thinking, but I started somewhere far far away 8-)

Great post. I did a lot of EIGRP work in the late ...

2012-01-27T04:11:04.006+01:00

Great post. I did a lot of EIGRP work in the late 90s and early to mid 00s. One gig I was on was convert a very large utility from a mixed routing protocol to all EIGRP. Ivan's book on EIGRP was critical to my design and migration approach. EIGRP is very fast on convergence and when I was reading about MPLS Fast Reroute it reminded of EIGRP's feasible successor ability but manually created. Also there is adjusting timers for EIGRP, debounce timers, carrier delays NSF and BFD. OSPF has these options too. Now throw MPLS into it, LSPs need a L3 routing protocol to connect and you have more "junk" on top of your topology to influence convergence. I even for one client used the variance unequal cost load balancing feature to solve a problem. I haven't done much with it lately and not sure of its status. I liked EIGRP and if they update it can still be very very powerful.

sheeshe it is 2012 where is that one protocol for all.

Okay where is the post for IPX/SPX where you can have a 10k node network and none of the subnetting issues etc and now since we can all have 1 to 10gig links who cares if it is a heavy protocol. ;)

In terms of convergence: 1. On the CPU based platf...

2012-01-27T00:32:55.456+01:00

In terms of convergence:
1. On the CPU based platforms there should be no difference between EIGRP and IP LFA.
2. On the distributed platforms IP LFA will be faster as HW FIB is ready for a switchover.

In terms of your recursive process maybe you started at the intra-AS BGP convergence topic or possibility of the fast path switchover when you were in the serious traffic jam?

My first thought before I hit "read more"...

2012-01-26T21:23:46.956+01:00

My first thought before I hit "read more" was - it depends". For OSPF, what if the two paths were equal costs? Then it would be immediate failover because the route already exist in the RIB.

My humble quess is that you wanted to cover topolo...

2012-01-26T20:45:12.704+01:00

My humble quess is that you wanted to cover topology predictibility and/or link-state microloops? I dump LDP FRR cause it's closely related.

But only about 5 people worldwide run MPLS inside ...

2012-01-26T20:24:17.920+01:00

But only about 5 people worldwide run MPLS inside an enterprise network, which is where UCMP would be quite valuable. Often enterprise sites each have a primary WAN link and slower, lower cost WAN link for redundancy.

Enterprises will most likely not implement MPLS en masse anytime soon, as the majority of installed and currently orderable enterprise gear doesn't support MPLS at all.

look like ipfrr per prefix was introduced back in ...

2012-01-26T19:43:56.000+01:00

look like ipfrr per prefix was introduced back in iox 3.5, may be they changed to per link in 3.9?
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.5/routing/configuration/guide/rc35rib.html#wp1088695

In theory, it would be possible. In practice? I do...

2012-01-26T16:27:01.083+01:00

In theory, it would be possible. In practice? I don't even know how much the EIGRP functionality is used ... and you can use MPLS-TE to get better results.

Also what do you think about theoretical possibili...

2012-01-26T09:38:12.822+01:00

Also what do you think about theoretical possibility of using alternate paths computed using LFA for OSPF and IS-IS for unequal cost load balancing (like it can be done with EIGRP)?

It's hard to predict EIGRP behavior without kn...

2012-01-26T09:29:44.392+01:00

It's hard to predict EIGRP behavior without knowing link costs. Given the same link attributes (bandwidth and delay) for all links in the triangular topology B won't be the feasible successor for X because B reported distance is not lower, but the same as A feasible distance.

Have you looked at Pierre's presentation (link...

2012-01-26T07:59:58.452+01:00

Have you looked at Pierre's presentation (link in the post)?

Ivan, great exercise. Can you also cover square to...

2012-01-26T07:55:11.433+01:00

Ivan, great exercise. Can you also cover square topology?

The LFA concept can be implemented in any link sta...

2012-01-26T07:47:52.870+01:00

The LFA concept can be implemented in any link state routing protocol, current Cisco IOS and Junos implementations are for IS-IS and OSPFv2.

Is this feature only for ospf v2 not v3?

2012-01-26T07:11:44.629+01:00

Is this feature only for ospf v2 not v3?