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... .//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 might
static routes than with OSPF. I'm not trying to be patronizing, but you don't mention many details, and some of the
ones for OSPF.
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
site? E.g. site1 and site2 both communicate to the central site via Metro Ethernet, and they also communicate to eachother via DSL.
If none of the above are true, then static routes would be better for you (for the remote area/s in question). E.g. area1 has multiple paths, so ospf is warranted; however, area2 has just one path so a static approach would usually be better.
Your language seems to indicate that OSPF is warranted (area0, area1, two ABRs). I am assuming you mean Area Border Router not Associative Based Routing (vs. OSPF). I am also assuming this is a non-public system (internal network, probably a MAN or WAN).
If so, without any further details, I would set it up for bandwidth/failover. Weight the paths appropriately. Keep it as simple as you can. OSPF can become a morass.
If you sketch your situation out more, we can be more helpful.... Campus? MAN? How public? Multi-pathed? Multi-homed? Multiple interlinks? Are there some lines with reliability problems where the lower bandwidth links are actually preferred? Do you have any decentralized concentration points that might have problems due to multiple remote sites shuttling traffic through it (due to multiple interlinks)?
--p
devang patel wrote:
Hi All,
I am not sure is this the good place to ask this question or not!!!
I am looking for feed back on having OSPF multi-area, lets say if you have multiple location in nonbackbone areas and those nonbackbone areas are connected with the one backbone area. For example: OSPF AREA1 has the connectivity to OSPF AREA0 using two ABR, so what is the optimum way to achieve the load balancing or load sharing for
be better off with details you omit are the crucial that bypass the central traffic entering or leaving
the area, what are the possible way to configure it?
regards Devang Patel