Re: OSPF packets, point-to-multipoint [7:20115]
Group, Can someone help me to understand or point me to a link so that I can get a definitive answer. Thanks. Routing TCP/IP, Vol. 1, Jeff Doyle : (a) Page # 417, 'Point-to-multipoint networks are a special configuration .. because the network are seen as point-to-point links, OSPF packets are multicast'. (b) Page # 451, 'On point-to-multipoint and virtual link networks, updates are unicasted to the interface addresses of adjacent neighbors'. (c) Page # 561, 'The OSPF point-to-multipoint network type treats the underlying as a collection of point-to-point links ..., and OSPF packets are multicast to the neighbor.' Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=20115&t=20115 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF packets, point-to-multipoint [7:20115]
Welcome to the world of OSPF. I trust you are prepared for a long and rewarding journey through the maze of possibilities. Much OSPF study is best done with a router at hand so you can set up various things and look and see how the protocol behaves. page 417: taken out of context. If you check how OSPF defaults on an NMBA interface or multipoint subinterface you will find the default is NMBA Serial2/3.1 is down, line protocol is down Internet Address 99.99.99.99/24, Area 0 Process ID 1000, Router ID 192.168.1.1, Network Type NON_BROADCAST, Cost: 48 Transmit Delay is 1 sec, State DOWN, Priority 1 No designated router on this network No backup designated router on this network Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5 one can change this interface to an OSPF point-to-multipoint by using the interface command ip ospf network point-to-multipoint, at which time you get Serial2/3.1 is down, line protocol is down Internet Address 99.99.99.99/24, Area 0 Process ID 1000, Router ID 192.168.1.1, Network Type POINT_TO_MULTIPOINT, Cost : 48 Transmit Delay is 1 sec, State DOWN, Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5 if you check RFC 2328, you will find that behaviour in terms of LSA's is different for both of these cases. As are the configuration contortions you must now perform. a couple of more quotes from the RFC are found below best wishes in your OSPF pursuits Chuck -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Alex Lee Sent: Sunday, September 16, 2001 9:30 AM To: [EMAIL PROTECTED] Subject: Re: OSPF packets, point-to-multipoint [7:20115] Group, Can someone help me to understand or point me to a link so that I can get a definitive answer. Thanks. Routing TCP/IP, Vol. 1, Jeff Doyle : (a) Page # 417, 'Point-to-multipoint networks are a special configuration .. because the network are seen as point-to-point links, OSPF packets are multicast'. (b) Page # 451, 'On point-to-multipoint and virtual link networks, updates are unicasted to the interface addresses of adjacent neighbors'. (c) Page # 561, 'The OSPF point-to-multipoint network type treats the underlying as a collection of point-to-point links ..., and OSPF packets are multicast to the neighbor.' -- CL inserted: >From the RFC: 12.4.1.4. Describing Point-to-MultiPoint interfaces For operational Point-to-MultiPoint interfaces, one or more link descriptions are added to the router-LSA as follows: o A single Type 3 link (stub network) is added with Link ID set to the router's own IP interface address, Link Data set to the mask 0x (indicating a host route), and cost set to 0. o For each fully adjacent neighbor associated with the interface, add an additional Type 1 link (point-to- point) with Link ID set to the Router ID of the neighboring router, Link Data set to the IP interface address and cost equal to the interface's configured output cost. And also: The IP destination address for the packet is selected as follows. On physical point-to-point networks, the IP destination is always set to the address AllSPFRouters. On all other network types (including virtual links), the majority of OSPF packets are sent as unicasts, i.e., sent directly to the other end of the adjacency. In this case, the IP destination is just the Neighbor IP address associated with the other end of the adjacency (see Section 10). The only packets not sent as unicasts are on broadcast networks; on these networks Hello packets are sent to the multicast destination AllSPFRouters, the Designated Router and its Backup send both Link State Update Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=20117&t=20115 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF packets, point-to-multipoint [7:20115]
Still do not understand, Building Scalable Cisco Networks, CiscoPress, page 123 " However,bcause the point-to-multipoint mode treats the network as a collection of point-to-point links, multicast hello packets discover neighbors dynamically, and statically configuring neighbors is not required." Routing TCP/IP, Vol. 1, page 433 "On broadcast and point-to-point network types, hellos are multicast to AllSPFRouters (224.0.0.5). On NBMA, point-to-multipoint, and virtual link network types, hello are unicast to individual neighbors. The implication of unicasting is that router must first learn of the existence of its neighbors either through manual configuration or an underlying mechanism such as Inverse ARP." What have I missed ? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=20132&t=20115 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF packets, point-to-multipoint [7:20115]
Hi Alex In point-to-multipoint network, a DR will be elected and the DR will multicast the message to all the ospf routers. Where else in point-to-point network, there are no DR selection and thats why either we rely on the inverse arp or manually configure it. William ""Alex Lee"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Still do not understand, > > Building Scalable Cisco Networks, CiscoPress, page 123 > " However,bcause the point-to-multipoint mode treats the network as a > collection of point-to-point links, multicast hello packets discover > neighbors dynamically, and statically configuring neighbors is not > required." > > Routing TCP/IP, Vol. 1, page 433 > "On broadcast and point-to-point network types, hellos are multicast to > AllSPFRouters (224.0.0.5). On NBMA, point-to-multipoint, and virtual link > network types, hello are unicast to individual neighbors. The implication of > unicasting is that router must first learn of the existence of its neighbors > either through manual configuration or an underlying mechanism such as > Inverse ARP." > > What have I missed ? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=20138&t=20115 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF packets, point-to-multipoint [7:20115]
without repeating my private response to your private mail, on NMBA networks, one usually configures OSPF neighbors. The whole NMBA issue is complex. There is the frame relay configuration, and then there is the OSPF configuration on top of that. You can have point to multipoint frame relay interfaces connected to physical, or point-to-point interfaces on the distant end. Inverse arp maps a remote IP address to the associated other side dlci. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Alex Lee Sent: Sunday, September 16, 2001 7:05 PM To: [EMAIL PROTECTED] Subject: Re: OSPF packets, point-to-multipoint [7:20115] Still do not understand, Building Scalable Cisco Networks, CiscoPress, page 123 " However,bcause the point-to-multipoint mode treats the network as a collection of point-to-point links, multicast hello packets discover neighbors dynamically, and statically configuring neighbors is not required." Routing TCP/IP, Vol. 1, page 433 "On broadcast and point-to-point network types, hellos are multicast to AllSPFRouters (224.0.0.5). On NBMA, point-to-multipoint, and virtual link network types, hello are unicast to individual neighbors. The implication of unicasting is that router must first learn of the existence of its neighbors either through manual configuration or an underlying mechanism such as Inverse ARP." What have I missed ? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=20144&t=20115 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF packets, point-to-multipoint [7:20115]
At 01:56 AM 9/17/01, Chuck Larrieu wrote: >without repeating my private response to your private mail, Please do repeat it!? ;-) Seriously, is the BSCN statement wrong?? "bcause the point-to-multipoint mode treats the network as a collection of point-to-point links, multicast hello packets discover neighbors dynamically, and statically configuring neighbors is not required." Priscilla >on NMBA >networks, one usually configures OSPF neighbors. The whole NMBA issue is >complex. There is the frame relay configuration, and then there is the OSPF >configuration on top of that. You can have point to multipoint frame relay >interfaces connected to physical, or point-to-point interfaces on the >distant end. Inverse arp maps a remote IP address to the associated other >side dlci. > >-Original Message- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of >Alex Lee >Sent: Sunday, September 16, 2001 7:05 PM >To: [EMAIL PROTECTED] >Subject: Re: OSPF packets, point-to-multipoint [7:20115] > > >Still do not understand, > >Building Scalable Cisco Networks, CiscoPress, page 123 >" However,bcause the point-to-multipoint mode treats the network as a >collection of point-to-point links, multicast hello packets discover >neighbors dynamically, and statically configuring neighbors is not >required." > >Routing TCP/IP, Vol. 1, page 433 >"On broadcast and point-to-point network types, hellos are multicast to >AllSPFRouters (224.0.0.5). On NBMA, point-to-multipoint, and virtual link >network types, hello are unicast to individual neighbors. The implication of >unicasting is that router must first learn of the existence of its neighbors >either through manual configuration or an underlying mechanism such as >Inverse ARP." > >What have I missed ? Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=20193&t=20115 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
