Tuesday, December 20, 2011

EIGRP TIMERS

Today i took a look at eigrp timers

OK to set the hello interface under the interface do
ip hello-interval "AS" "seconds" - the default will depend on the underlying media it is typically 5 seconds
but for nbma wan connections it is 60 seconds
Hold time - Is advertised in the hello packet it has a different  meaning than in ospf. In eigrp the hold time
            is you telling the neighbor how long the neighbor should wait before declaring the neighbor down. Not
            how long you will wait. When you configure hold time it will not affect you locally it will affect your              neighbor

ip hold-time eigrp "AS" "seconds"  typically 3 times the hello interval so 15 seconds typically or 180 seconds on wan nmba interface

TIMERS DO NOT HAVE TO MATCH TO FORM ADJACENCY

LAB
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We will have  sw3 connected to both r4 and r5 running eigrp we will change the the hello and hold + watch see how it affects
r4#sh ip eigrp int
IP-EIGRP interfaces for process 1
                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Fa0/0              2        0/0       430       0/1            0           0
r4#sh ip eigrp int detail
IP-EIGRP interfaces for process 1
                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Fa0/0              2        0/0       430       0/1            0           0
  Hello interval is 5 sec
  Next xmit serial <none>
  Un/reliable mcasts: 0/0  Un/reliable ucasts: 1/30
  Mcast exceptions: 0  CR packets: 0  ACKs suppressed: 7
  Retransmissions sent: 8  Out-of-sequence rcvd: 1
  Authentication mode is not set
we can see the hello interval is 5 seconds on r4

i will change the hello interval
r4(config)#int fa0/0
r4(config-if)#ip hello-interval eigrp 1 10
r4(config-if)#

r4#sh ip eigrp int det
IP-EIGRP interfaces for process 1
                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Fa0/0              2        0/0       430       0/1            0           0
  Hello interval is 10 sec
  Next xmit serial <none>
  Un/reliable mcasts: 0/0  Un/reliable ucasts: 1/30
  Mcast exceptions: 0  CR packets: 0  ACKs suppressed: 7
  Retransmissions sent: 8  Out-of-sequence rcvd: 1
  Authentication mode is not set

ok so it is changed now to 10 seconds the hello

i can see on r1 the hold time is still at the default 15 seconds
switch1#sh ip eigrp nei
IP-EIGRP neighbors for process 1
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq Type
                                            (sec)         (ms)       Cnt Num
1   10.229.254.4            Po2                6 00:13:24    1  3000  0  22
0   10.229.254.2            Po2               12 00:14:20    9   200  0  14
switch1#sh ip eigrp nei
IP-EIGRP neighbors for process 1
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq Type
                                            (sec)         (ms)       Cnt Num
1   10.229.254.4            Po2               14 00:13:25    1  3000  0  22
0   10.229.254.2            Po2               11 00:14:21    9   200  0  14
it keeps starting at 14 and goes down to lowish 5-6 seconds
so the hold time is still at 15 but the hello is 10
i changed the hello on  r4 to 15 seconds

we can see now on s1
switch1#sh ip eigrp ne
IP-EIGRP neighbors for process 1
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq Type
                                            (sec)         (ms)       Cnt Num
1   10.229.254.4            Po2                1 00:16:09    1  3000  0  22
0   10.229.254.2            Po2               13 00:17:05    9   200  0  14
switch1#sh ip eigrp ne
IP-EIGRP neighbors for process 1
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq Type
                                            (sec)         (ms)       Cnt Num
1   10.229.254.4            Po2               14 00:16:12    1  3000  0  22
0   10.229.254.2            Po2               14 00:17:07    9   200  0  14
switch1#sh ip eigrp ne

it keeps going very close to the dead hold time

ok on r4 i will change hold interval to
r4(config-if)#ip hold-time eigrp 1 40

switch1#sh ip eigrp neigh
IP-EIGRP neighbors for process 1
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq Type
                                            (sec)         (ms)       Cnt Num
1   10.229.254.4            Po2               37 00:01:33    1  4500  0  32
the hold time is gone high 40 seconds as i edited on r4 so the point is that changing the hold time on r4 will affect the neighboring routers not local routers.

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