nanog mailing list archives
Re: OSPF with Multiple ABR & ASBR
From: isabel dias <isabeldias1 () yahoo com>
Date: Fri, 14 Nov 2008 08:06:30 -0800 (PST)
Patel, I would suggest you to read a few things about the path selection algoritm....as if i understand your words you are asking for an issue on LSA type 4 rather than multiple AS and therefore LSA type 5 /7-ASBR prefer backbone intra-area paths over inter-area paths.... Excerpted from RFC 16.4.1...- When multiple intra-AS paths are available to ASBRs/forwarding addresses some rules using different costs apply when the same ASBR is reachable through multiple areas, or when trying to decide which of several AS-external-LSAs should be preferred. In the former case the paths all terminate at the same ASBR, while in the latter the paths terminate at separate ASBRs/forwarding addresses. http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080124c7d.shtml .//ID --- On Fri, 11/14/08, devang patel <devangnp () gmail com> wrote:
From: devang patel <devangnp () gmail com> Subject: Re: OSPF with Multiple ABR & ASBR To: "Patrick Darden" <darden () armc org> Cc: nanog () nanog org Date: Friday, November 14, 2008, 4:52 PM Sorry about that!!! 1. Do these remote areas have multiple paths to the central area for failover? E.g. a 10Mbps Metro Ethernet primary link, and a 1.5Mbps DSL secondary? 2. Does the central area have multiple routers for failover? E.g. a Cisco 7200 for the incoming Metro Ethernet primary connections, and a Cisco 3660 for the slower secondary connections? 3. Are there any tie-ins between the remote sites that bypass the central site? E.g. site1 and site2 both communicate to the central site via Metro Ethernet, and they also communicate to eachother via DSL. Answers: I have two T1 line to the non-backbone area and both T1s are terminated to the two different routers on non-backbone area as well as to backbone area, and I dont want to achieve primary and secondary role, I want to go for the load sharing kind of scenario. All sites are connected with the central site. ABR means Area border router only. I am attaching one generalized diagram, please look at that one. Now I want to achieve the load balancing between the traffic going from R1 to R8, I want to achieve some of the networks on R1 should be reachable via R2 and some of them via R3 for the traffic coming from the R8. assume all links are same. regards Devang Patel On Fri, Nov 14, 2008 at 9:29 AM, Patrick Darden <darden () armc org> wrote:First, without any details, it sounds like you mightbe better off withstatic routes than with OSPF. I'm not trying tobe patronizing, but youdon't mention many details, and some of thedetails you omit are the crucialones for OSPF. 1. Do these remote areas have multiple paths to thecentral area forfailover? E.g. a 10Mbps Metro Ethernet primary link,and a 1.5Mbps DSLsecondary? 2. Does the central area have multiple routers forfailover? E.g. a Cisco7200 for the incoming Metro Ethernet primaryconnections, and a Cisco 3660for the slower secondary connections? 3. Are there any tie-ins between the remote sitesthat bypass the centralsite? E.g. site1 and site2 both communicate to thecentral site via MetroEthernet, and they also communicate to eachother viaDSL.If none of the above are true, then static routeswould be better for you(for the remote area/s in question). E.g. area1 hasmultiple paths, so ospfis warranted; however, area2 has just one path so astatic approach wouldusually be better. Your language seems to indicate that OSPF is warranted(area0, area1, twoABRs). I am assuming you mean Area Border Router notAssociative BasedRouting (vs. OSPF). I am also assuming this is anon-public system(internal network, probably a MAN or WAN). If so, without any further details, I would set it upforbandwidth/failover. Weight the paths appropriately.Keep it as simple asyou can. OSPF can become a morass. If you sketch your situation out more, we can be morehelpful.... Campus?MAN? How public? Multi-pathed? Multi-homed?Multiple interlinks? Arethere some lines with reliability problems where thelower bandwidth linksare actually preferred? Do you have any decentralizedconcentration pointsthat might have problems due to multiple remote sitesshuttling trafficthrough it (due to multiple interlinks)? --p devang patel wrote:Hi All, I am not sure is this the good place to ask thisquestion or not!!!I am looking for feed back on having OSPFmulti-area, lets say if you havemultiple location in nonbackbone areas and thosenonbackbone areas areconnected with the one backbone area. For example:OSPF AREA1 has theconnectivity to OSPF AREA0 using two ABR, so whatis the optimum way toachieve the load balancing or load sharing fortraffic entering or leavingthe area, what are the possible way to configureit?regards Devang Patel
Current thread:
- OSPF with Multiple ABR & ASBR devang patel (Nov 14)
- Re: OSPF with Multiple ABR & ASBR Patrick Darden (Nov 14)
- Re: OSPF with Multiple ABR & ASBR devang patel (Nov 14)
- Re: OSPF with Multiple ABR & ASBR isabel dias (Nov 14)
- RE: OSPF with Multiple ABR & ASBR Darden, Patrick S. (Nov 14)
- RE: OSPF with Multiple ABR & ASBR Steve Dalberg (Nov 14)
- Re: OSPF with Multiple ABR & ASBR devang patel (Nov 14)
- Re: OSPF with Multiple ABR & ASBR Patrick Darden (Nov 14)