In EIGRP introduction tutorial, I think the AD value advertised by R3 to R1 should be 9 instead of 12( how could you say 12 ) and in return AD advertised by R1 to R3( If advertisements possible b/w neighbors it must be FD to reach Destination) is 12 don’t understandable, why R1 advertise (FD or AD=12) to R3 , you has not mentioned anywhere the neighbors will advertise the AD and FD to each other if this is possible then R4 advertise Ad=9 to R3 and in return R3 will advertise same to R4 ?
Query pertaining to eigrp neighbor adjacency topic,
How R2 sending update message before hello message ?, I think first of all they form adjacency by sending and receiving hellos to each other then later will send update messages ?
When we use concept of variance then in this case FD of FS less than FD of S then according to this FS should be successor and like this concept of load balancing doesn’t set fit b/c now this is a successor and this will be in routing table?
Post using variance will successor be successor or the one which will have lower FD post variance like Feasible successor ?
According to topology you using and command output sh ip route 5.5.5.5 , we can see update received in order like 192.168.14.4, 192.168.13.3 and then successor ?
192.168.14.4, from 192.168.14.4, 00:00:19 ago, via Serial2/0
Route metric is 2300416, traffic share count is 17
Total delay is 25100 microseconds, minimum bandwidth is 1544 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
192.168.13.3, from 192.168.13.3, 00:00:19 ago, via Ethernet1/0
Route metric is 412160, traffic share count is 92
Total delay is 6100 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
This is a typo indeed, I just fixed this in the post.
EIGRP will always start with the neighbor adjacency so the first packets that are exchanged are hello packets. In that lesson, I only showed the UPDATE messages from R2 instead of the entire debug because it wasn’t relevant.
That’s a good question…just looking at the acronyms, it’s not easy to tell. I tried to look it up in the master index which covers debug eigrp packets.
They don’t explain it there. I also looked at an EIGRP packet to see if it matches any of the items you find in a packet. This shows the AS number, flags, and sequence number but that’s pretty much it.
These seem to be some internal EIGRP things but they don’t explain it anywhere. In the output above, you also see some references to things like “ddbQ” under the Internal process states.
Keep in mind that variance doesn’t influence the S and FS selection. First we use select the S and FS(es), afterward we can use the variance command to insert FS(es) into the routing table.
why are we getting different out while using summary-address and summary metric command for summarization ?
R2#show ip route eigrp 172.16.0.0/23 is subnetted, 1 subnets D 172.16.0.0 [90/30720] via 192.168.12.1, 00:00:53, FastEthernet0/0
R2#show ip route eigrp 172.16.0.0/24 is subnetted, 2 subnets D 172.16.0.0 [90/2562816] via 192.168.12.1, 00:02:28, FastEthernet0/0 D 172.16.1.0 [90/2562816] via 192.168.12.1, 00:02:28, FastEthernet0/0
I think in both output there must be 172.16.0.0/23 subnetted, 1 subnets … and let’s suppose 172.16.0.0 subnetted in subnets in 2nd output but it should display 172.16.0.0/23 instead of 172.16.0.0/24 ?
Could you fully explain concept of null 0 using topology and for which network ( from which router) ?
In second method we are using 192.168.23.0 as a default n/w as a given topology means if we want to go only this n/w we can go from 192.168.12.2 as per R1 perspective not like default route which states that if we want to go any n/w with any mask follow given next hop ?
If there are two routes to a particular destination and their cost is equal, you will have two successors, and both routes will be placed in the routing table. Equal cost load balancing will take place between those two routes. In order to make one of the two a FS, you must adjust the cost by adjusting one of the K values to make one route preferable. Take a look at this lesson for more information:
This is the default behaviour of EIGRP and it is based on rigorous testing to find the best parameters that work for most topologies.
The unit is “tens of microseconds”. So a value of 40 is 400 microseconds. More info can be found at this lesson:
This one may be an error in the output. I will let Rene know and get back to you…
You can find out about the Null0 exit interface at the following lesson:
Here’s another example of how it is used in BGP:
The ip default-network command essentially tells the router to route all traffic that doesn’t match any other routing table entry, as if it was destined for 192.168.23.0. In other words, a packet with a destination address of 123.123.123.5 (which is not in the routing table) will be routed as if it was an address in the 192.168.23.0/24 network.
Thanks a lot Laz, I know sometimes you take time to revert back but after all you or Rene team give responses, Your response making me trust on NL and drive me to use Network Lessons more and more.
Hello,
I am trying to understand the below paragraph.
“Sia Status (Stuck in Active): This is a bad one…it means that EIGRP has not received a reply to a query packet from one of the neighbors within the allowed time (about 3 minutes). When this happens, EIGRP will drop the neighbor adjacency, and it will be stuck in active. More on this later!”
Now my question is, If a network is unreachable in EIGRP then it will send a query packet to its neighbors. If the router does not receive any reply for that query then why would it drop its neighbor adjacency ???
I’m not sure where you got that particular quote, but it seems that even though it is accurate, it is out of date. Before IOS 12.1, the adjacency would be dropped if after 3 minutes a reply to a query was not received. ALl the routes learned from that adjacency would also be removed. After IOS 12.1 however, the process has changed to eliminate the dropping of the adjacency. The difference is that now we have a new type of query called an SIA query.
You can find out the whole process in more detail in the following lesson: