Can I prevent OSPF from advertising a specific network on an interface
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From: ve7eje on 18 Mar 2010 10:47 Is there a way to tell OSPF to not advertise a specific network on a spefic interface without stopping the adverts of other networks? Example Router has 5 interfaces F1 is a link to another router F2 is a link to another router F3 = netB F4 = netC F5 = netD I need nets BCD to be advertised out F1 and F2 but not each other. Similarly I need nets learned on F1 and F2 to be advertised on F1, F2 and F3 only. I've looked at the passive interface command but I don't think it will do what I want. Thanks -Rob-
From: Thrill5 on 18 Mar 2010 19:20 You need to use a distribute list on the interface. "ve7eje" <ve7eje(a)gmail.com> wrote in message news:0b5cfd04-7d49-4aca-b0bf-f9801fe590f7(a)g28g2000prb.googlegroups.com... > Is there a way to tell OSPF to not advertise a specific network on a > spefic interface without stopping the adverts of other networks? > Example > Router has 5 interfaces > F1 is a link to another router > F2 is a link to another router > F3 = netB > F4 = netC > F5 = netD > > I need nets BCD to be advertised out F1 and F2 but not each other. > Similarly I need nets learned on F1 and F2 to be advertised on F1, F2 > and F3 only. > > I've looked at the passive interface command but I don't think it will > do what I want. > > Thanks -Rob-
From: bod43 on 19 Mar 2010 00:44 On 18 Mar, 23:20, "Thrill5" <nos...(a)somewhere.com> wrote: > You need to use a distribute list on the interface. > > "ve7eje" <ve7...(a)gmail.com> wrote in message > > news:0b5cfd04-7d49-4aca-b0bf-f9801fe590f7(a)g28g2000prb.googlegroups.com... > > > Is there a way to tell OSPF to not advertise a specific network on a > > spefic interface without stopping the adverts of other networks? > > Example > > Router has 5 interfaces > > F1 is a link to another router > > F2 is a link to another router > > F3 = netB > > F4 = netC > > F5 = netD > > > I need nets BCD to be advertised out F1 and F2 but not each other. > > Similarly I need nets learned on F1 and F2 to be advertised on F1, F2 > > and F3 only. > > > I've looked at the passive interface command but I don't think it will > > do what I want. > Sorry Thrill5, but I suspect that is not the whole story. In a word - no. Due to the architecture of OSPF it is not possible to so restrict the advertisment of networks. Under some circumstances it is possible to filter routes, e.g. when re-distributing between OSPF processes, perhaps between OSPF Areas?, however in general this is not possible. OSPF works by every router sending out Link State Advertisments (LSA). These represent the network topology. All the routers in an area eventually receive all of the LSAs as sent by every router in the area. Each router then uses the LSAs to construct a topology database. The routing tables in each router are then calculated independently by each router from its own copy of the topology database. The key thing is that every router in a area *must* have the same topology database. Well maybe ends up with the same topology database is more accurate:) So if your "router" has knowledge of the topology it will send it to all of the other routers. You can use EIGRP since it works by sending routes which you can of course effectively filter. Perhaps you could find a solution with multiple OSPF processes and redistribution between them. You can apply filters to the redistribution process since they are simple routes. I may have a think about it later. Seems pretty likely at first glance.
From: John Agosta on 19 Mar 2010 15:18 "bod43" <Bod43(a)hotmail.co.uk> wrote in message news:469b4f59-bd17-4b16-a652-e005da06a363(a)r27g2000yqn.googlegroups.com... > On 18 Mar, 23:20, "Thrill5" <nos...(a)somewhere.com> wrote: >> You need to use a distribute list on the interface. >> >> "ve7eje" <ve7...(a)gmail.com> wrote in message >> >> news:0b5cfd04-7d49-4aca-b0bf-f9801fe590f7(a)g28g2000prb.googlegroups.com... >> >> > Is there a way to tell OSPF to not advertise a specific network on a >> > spefic interface without stopping the adverts of other networks? >> > Example >> > Router has 5 interfaces >> > F1 is a link to another router >> > F2 is a link to another router >> > F3 = netB >> > F4 = netC >> > F5 = netD >> >> > I need nets BCD to be advertised out F1 and F2 but not each other. >> > Similarly I need nets learned on F1 and F2 to be advertised on F1, F2 >> > and F3 only. >> >> > I've looked at the passive interface command but I don't think it will >> > do what I want. >> > > Sorry Thrill5, but I suspect that is not the whole story. > > In a word - no. Due to the architecture of OSPF it is not > possible to so restrict the advertisment of networks. > > Under some circumstances it is possible to filter routes, > e.g. when re-distributing between OSPF processes, > perhaps between OSPF Areas?, however > in general this is not possible. > > OSPF works by every router sending out Link State > Advertisments (LSA). These represent the network > topology. All the routers in an area eventually receive > all of the LSAs as sent by every router in the area. > Each router then uses the LSAs to construct a > topology database. The routing tables in each router > are then calculated independently by each router > from its own copy of the topology database. > > The key thing is that every router in a area *must* > have the same topology database. Well maybe > ends up with the same topology database is more > accurate:) > > So if your "router" has knowledge of the topology it will send it > to all of the other routers. > > You can use EIGRP since it works by sending routes > which you can of course effectively filter. > > Perhaps you could find a solution with multiple OSPF > processes and redistribution between them. You can > apply filters to the redistribution process since they are > simple routes. I may have a think about it later. Seems > pretty likely at first glance. > > An outbound distribute list will not work with OSPF, however, I'm pretty sure an inbound list will be able to filter unwanted routes.
From: John Agosta on 21 Mar 2010 12:51
"John Agosta" <jagosta(a)wideopenwest.com> wrote in message news:gP6dnW5hIZ1kUD7WnZ2dnUVZ_uidnZ2d(a)wow.com... > > "bod43" <Bod43(a)hotmail.co.uk> wrote in message > news:469b4f59-bd17-4b16-a652-e005da06a363(a)r27g2000yqn.googlegroups.com... >> On 18 Mar, 23:20, "Thrill5" <nos...(a)somewhere.com> wrote: >>> You need to use a distribute list on the interface. >>> >>> "ve7eje" <ve7...(a)gmail.com> wrote in message >>> >>> news:0b5cfd04-7d49-4aca-b0bf-f9801fe590f7(a)g28g2000prb.googlegroups.com... >>> >>> > Is there a way to tell OSPF to not advertise a specific network on a >>> > spefic interface without stopping the adverts of other networks? >>> > Example >>> > Router has 5 interfaces >>> > F1 is a link to another router >>> > F2 is a link to another router >>> > F3 = netB >>> > F4 = netC >>> > F5 = netD >>> >>> > I need nets BCD to be advertised out F1 and F2 but not each other. >>> > Similarly I need nets learned on F1 and F2 to be advertised on F1, F2 >>> > and F3 only. >>> >>> > I've looked at the passive interface command but I don't think it will >>> > do what I want. >>> >> >> Sorry Thrill5, but I suspect that is not the whole story. >> >> In a word - no. Due to the architecture of OSPF it is not >> possible to so restrict the advertisment of networks. >> >> Under some circumstances it is possible to filter routes, >> e.g. when re-distributing between OSPF processes, >> perhaps between OSPF Areas?, however >> in general this is not possible. >> >> OSPF works by every router sending out Link State >> Advertisments (LSA). These represent the network >> topology. All the routers in an area eventually receive >> all of the LSAs as sent by every router in the area. >> Each router then uses the LSAs to construct a >> topology database. The routing tables in each router >> are then calculated independently by each router >> from its own copy of the topology database. >> >> The key thing is that every router in a area *must* >> have the same topology database. Well maybe >> ends up with the same topology database is more >> accurate:) >> >> So if your "router" has knowledge of the topology it will send it >> to all of the other routers. >> >> You can use EIGRP since it works by sending routes >> which you can of course effectively filter. >> >> Perhaps you could find a solution with multiple OSPF >> processes and redistribution between them. You can >> apply filters to the redistribution process since they are >> simple routes. I may have a think about it later. Seems >> pretty likely at first glance. >> >> > > An outbound distribute list will not work with OSPF, however, I'm pretty > sure an inbound list will be able to filter unwanted routes. > As to suggesting something to help with your scenario, and if you 'must' use OSPF, you can try running each interface under a different OSPF process, and control redistribution of your routing information between your processes with a distribute/prefix list..... -ja |