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 <[EMAIL PROTECTED]> wrote: > From: devang patel <[EMAIL PROTECTED]> > Subject: Re: OSPF with Multiple ABR & ASBR > To: "Patrick Darden" <[EMAIL PROTECTED]> > 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 > <[EMAIL PROTECTED]> wrote: > > > > > First, without any details, it sounds like you might > be better off with > > static routes than with OSPF. I'm not trying to > be patronizing, but you > > don't mention many details, and some of the > details you omit are the crucial > > 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 > 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. > > > > 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 > traffic entering or leaving > >> the area, what are the possible way to configure > it? > >> > >> regards > >> Devang Patel > >> > >> > >
