Steve, > Yes, it is an Internet ASBR, there are others, and its only purpose is to > advertise a default route + local DMZ into OSPF. The ASBR would get a > default route from BGP. In turn the ISP is advertising a default route via > BGP into the outside router. The plan is that if the ISP stops advertising > at this point, then the default route advertisement from one of the other > ISP connection points will take over. I see it that it really depends on > how much equipment is between the real backbone and the ISP connection.
I had a similar question like you, see mail below, where a Cisco Press author proposes to connect an (Internet) ASBR to the OSPF backbone area. It's good to hear that there doesn't seem to be a general design guideline...Lots of freedom... ;-) Eric ----- Original Message ----- From: "ericbrouwers" To: Sent: Monday, January 27, 2003 9:05 PM Subject: Re: ASBR in backbone area?? [7:61614] > I do not foresee any problems, maybe others do? > > I just find the design guideline below too strict. In small networks there > may be only one OSPF area, but larger networks typically have more areas. > Connections to the Internet or to other external networks like corporate > networks, tend to be on routers in the edge/distribution layer of the > network. Those routers are in OSPF areas different to zero (al least in the > OSPF designs I have seen so far). > > Also Cisco advises to connect 'the Internet' in the distribution layer (in > the DCN and CID courses). > > So for example for designs where three or four core routers are fully meshed > in OSPF area 0, and the surrounding distribution layer devices belong the > area x, with x/=0, the ASBR will not be connected to area 0. > > I also noticed a similar question in the thread called "OSPF to Internet". > > Eric Brouwers > > ----- Original Message ----- > From: > To: "ericbrouwers" > Sent: Thursday, January 23, 2003 6:05 PM > Subject: Re: ASBR in backbone area?? [7:61614] > > > > > > What kind of problem do you see putting the ASBR on the backbone area? > > > > Just to think about. > > > > > > > > > > > > "ericbrouwers" @groupstudy.com em 22/01/2003 > > 18:45:17 > > > > Favor responder a "ericbrouwers" > > > > Enviado Por: [EMAIL PROTECTED] > > > > > > Para: [EMAIL PROTECTED] > > cc: > > > > Assunto: ASBR in backbone area?? [7:61614] > > > > > > Hi there, > > > > Cisco Press' CCNP Routing Exam Certification Guide advises to place an > ASBR > > in > > the backbone area (p. 290, chapter 6): > > > > "... If there is any redistribution between other protocols to OSPF on a > > router, it will be an ASBR. Although you can place this router anywhere in > > the > > OSPF hierarchical design, it should reside in the backbone area. Because > > any > > traffic leaving the OSPF domain will also likely leave the router's area, > > it > > makes sense to place the ASBR in a central location that all traffic > > leaving > > its area must traverse..." > > > > I find this a strange design guideline. I would rather prefer to connect > an > > external network to the edge/distribution layer in an OSPF area different > > to > > the backbone area. As a consequence redistribution would happen outside > the > > backbone area... > > > > What's your view on this? > > > > Eric Brouwers Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=61982&t=61823 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
