eigrp passive interface...

won't send eigrp messages or establish eigrp neighborship, but it is an active interface...

r2(config-router)#do sh ip eigrp int
EIGRP-IPv4 Interfaces for AS(1)
                              Xmit Queue   PeerQ        Mean   Pacing Time   Multicast    Pending
Interface              Peers  Un/Reliable  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Se1/0                    1        0/0       0/0           7       5/195        231           0
Se1/1                    1        0/0       0/0          18       2/97         169           0
Lo0                      0        0/0       0/0           0       0/0            0           0
Se2/1                    1        0/0       0/0          15       0/23          91           0
Se2/2                    1        0/0       0/0          13       1/48          88           0
Se2/3                    1        0/0       0/0          12       5/190        246           0
Se1/2                    1        0/0       0/0          23       0/15         119           0

changing an interface to passive drops it out of eigrp...

r2(config-if)#router eigrp 1
r2(config-router)#passive-inter s1/2
r2(config-router)#
*Sep 13 05:44:04: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 172.20.15.6 (Serial1/2) is down: interface passive
r2(config-router)#do sh ip eigrp int
EIGRP-IPv4 Interfaces for AS(1)
                              Xmit Queue   PeerQ        Mean   Pacing Time   Multicast    Pending
Interface              Peers  Un/Reliable  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Se1/0                    1        0/0       0/0           8       5/195        219           0
Se1/1                    1        0/0       0/0          18       2/97         161           0
Lo0                      0        0/0       0/0           0       0/0            0           0
Se2/1                    1        0/0       0/0          17       0/23          79           0
Se2/2                    1        0/0       0/0           9       1/48          96           0
Se2/3                    1        0/0       0/0          15       5/190        246           0

but it is still up up...

r2(config-router)#do sh int s1/2
Serial1/2 is up, line protocol is up
  Hardware is M4T
  Internet address is 172.20.15.5/30

and can be communicated with...

r3#ping 172.20.15.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.20.15.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/12 ms


and ip proto will display it as passive...

r2(config-router)#do sh ip proto    
*** IP Routing is NSF aware ***

Routing Protocol is "eigrp 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Default networks flagged in outgoing updates
  Default networks accepted from incoming updates
  EIGRP-IPv4 Protocol for AS(1)
    Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
    NSF-aware route hold timer is 240
    Router-ID: 172.20.10.1
    Topology : 0 (base)
      Active Timer: 3 min
      Distance: internal 90 external 170
      Maximum path: 4
      Maximum hopcount 100
      Maximum metric variance 7

  Automatic Summarization: disabled
  Maximum path: 4
  Routing for Networks:
    172.20.0.0
  Passive Interface(s):
    Serial1/2
  Routing Information Sources:
    Gateway         Distance      Last Update
    172.20.15.22          90      00:03:29
    172.20.15.18          90      00:03:29
    172.20.15.6           90      00:07:34
    172.20.15.2           90      00:03:29
    172.20.15.14          90      00:03:29
    172.20.15.10          90      00:03:29
  Distance: internal 90 external 170

passive interface

i set up vlan 100 and 200 on dls1 as  passive interfaces so as to not advertise routes from those interfaces...


this is very exciting...  see below

dls2#sh ip route
Codes: (omitted)
Gateway of last resort is not set

     1.0.0.0/24 is subnetted, 1 subnets
D       1.1.1.0 [90/130816] via 172.16.1.1, 00:00:03, Vlan1
     172.16.0.0/24 is subnetted, 4 subnets
C       172.16.255.0 is directly connected, Vlan300
C       172.16.200.0 is directly connected, Vlan200
C       172.16.1.0 is directly connected, Vlan1
C       172.16.100.0 is directly connected, Vlan100
     10.0.0.0/24 is subnetted, 1 subnets
D       10.1.1.0 [90/2170112] via 172.16.1.10, 00:00:03, Vlan1
D    192.168.1.0/24 [90/28416] via 172.16.1.1, 00:00:03, Vlan1
dls2#

dls1#sh ip eigrp interfaces
EIGRP-IPv4:(1) interfaces for process 1

                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Vl1                2        0/0         1       0/1           50           0
Lo0                0        0/0         0       0/1            0           0
Fa0/24             0        0/0         0       0/1            0           0
dls1#

dls1#sh ip proto
*** IP Routing is NSF aware ***

Routing Protocol is "eigrp 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Default networks flagged in outgoing updates
  Default networks accepted from incoming updates
  Redistributing: eigrp 1

Address Family Protocol EIGRP-IPv4:(1)
  EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  EIGRP maximum hopcount 100
  EIGRP maximum metric variance 1
  EIGRP NSF-aware route hold timer is 240
  Topologies : 0(base)

  Automatic network summarization is not in effect
  Maximum path: 4
  Routing for Networks:
    1.1.1.0/24
    172.16.1.0/24
    172.16.100.0/24
    172.16.200.0/24
    192.168.1.0
  Passive Interface(s):
    Vlan100
    Vlan200
  Routing Information Sources:
    Gateway         Distance      Last Update
    172.16.200.2          90      00:13:56
    172.16.1.10           90      00:07:40
    172.16.1.2            90      00:07:40
    172.16.100.2          90      00:16:57
  Distance: internal 90 external 170

dls1#

then i added them back... note the differences...

dls2#sh ip route
Codes:

Gateway of last resort is not set

     1.0.0.0/24 is subnetted, 1 subnets
D       1.1.1.0 [90/130816] via 172.16.200.1, 00:00:03, Vlan200
                [90/130816] via 172.16.100.1, 00:00:03, Vlan100
                [90/130816] via 172.16.1.1, 00:00:03, Vlan1
     172.16.0.0/24 is subnetted, 4 subnets
C       172.16.255.0 is directly connected, Vlan300
C       172.16.200.0 is directly connected, Vlan200
C       172.16.1.0 is directly connected, Vlan1
C       172.16.100.0 is directly connected, Vlan100
     10.0.0.0/24 is subnetted, 1 subnets
D       10.1.1.0 [90/2170112] via 172.16.1.10, 00:00:03, Vlan1
D    192.168.1.0/24 [90/28416] via 172.16.200.1, 00:00:05, Vlan200
                    [90/28416] via 172.16.100.1, 00:00:05, Vlan100
                    [90/28416] via 172.16.1.1, 00:00:05, Vlan1
dls2#

the command is:

dls1(config)#router eigrp 1
dls1(config-router)#passive-inter vlan 100

get in the habit of using this command for obvious reasons...

dls1(config-router)#eigrp ?
  event-log-size         Set EIGRP maximum event log entries
  event-logging          Log EIGRP routing events
  log-neighbor-changes   Enable/Disable EIGRP neighbor logging
  log-neighbor-warnings  Enable/Disable EIGRP neighbor warnings
  router-id              router id for this EIGRP process
  stub                   Set EIGRP as stubbed router

dls1(config-router)#eigrp log-neighbor-ch

if there is no neighbor hanging off the interface the guidance is to make it passive... for security or some shit...whatever...