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| JayDot 2003-09-05, 2:51 pm |
| Hey Guys a Couple Question
1st) When use OSPF Does the Autonomus system # have to be same in all router???
Ex ospf 200 should all my router running ospf have ospf 200 can I run two diffrent autonomus system EXample ospf 200 and ospf 201...
2nd) DR/BDR How many DR/BDR can there be in an area or network??
for example area0 will have DR/BDR aresa 1 will have dr/bdr????
or Each Network advertise will have BDR/DR
192.168.1.0 or 10.0.0.0 or 172.16.0.0
Thanx for any Links or Post/Replys | |
| edmonds_robert 2003-09-05, 5:39 pm |
| 1. All routers in the same area will be configured with the same AS number. However, ABR and ASBR will have two areas configured, to route between the areas.
2. One DR and one BDR per area, I believe. Not positive about that one, though.
Robert | |
| SureshHomepage 2003-09-06, 12:16 am |
| Hi,
What you put after 'router ospf' command is 'process id' and not the 'Autonomous System (AS)' as you mentioned.
The process ID is purely local to the router and has no value outside the router. Any two OSPF neighboring routers can have different OSPF process IDs, unlike EIGRP where the routers need to have the same AS. You can run multiple OSPF processes on the same router.
About the DR/BDR, there can be only one set of them can exist in an Broadcast/NBMA network. The number of DR/BDR set purely depends on how many broadcast/NBMA cloud you are creating. In reality it depends on the geography of sites, type of link between the sites, and decretions from the network mangement personnel and many a times simply by the IP subnets the routers are sharing.
Hope this would help a bit! | |
| JayDot 2003-09-06, 2:30 pm |
| Thank You for Clearing That Up
So OSPF Process ID# Doesnt Have to Be the Same in All Router for Them to Share Routing INFO, Unlike EIGRP like u said??
Is The Correct???
and DR and BDR all Depends on The Network Topology, and the Number of Subnet you have Configured..
I.E for every Network I advertise
10.0.0.0
172.16.0.0
192.168.22.0
So in the case I Would Have 3 Dr and BDR | |
| SureshHomepage 2003-09-06, 7:59 pm |
| You are correct! you got the point JayDot!! | |
| lamchung 2003-09-07, 8:11 pm |
| Suresh is corrected but I like to make it clear and summary here so it easy for every one to remember OSPF concept.
There is no Autonomous System number in OSPF configuration or command. It is the process ID that define when you configure ospf
eg. Router OSPF 109, where 109 is the process ID and not autonomoous system number.
Designator and Backup Designator are router formed on a Broadcast mutiaccess network such as LAN. they are there to reduce the number of adjacency and muticast flooding. eg. all routers on a LAN only established adjacency with both the DR and BDR routers. and only the DR router send out link state update to all other ordinary routers on the LAN network when there is a link state change. The BDR just listen and do nothing unless the DR down in which case it take over the DR router function by promote it self to become a DR. Then it start multicast out link state update for its LAN.
So if you ask how many DR or DBR routers in an OSPF area. The correct answer is depend on how many LAN network or Broadcast Subnet you have in your OSPF. Each boardcast subnet will have one DR and one BDR formed. Note that, there will be no BDR when there is only router on any particular subnet as this router certainly be the DR for the subnet. | |
| JayDot 2003-09-08, 9:18 am |
| I LUV This Website.........
What Can't I Learn Here..............
Thanx Guys... |
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