EIGRP named mode "passive-interface default" vs "af-interface default shutdown" and Virtual-Template

    As you probably know, EIGRP named mode is a new style standard for EIGRP configuration in current IOS versions. So I would like to note some interesting points on configuration.
May be not so interesting really, but this significant difference was noted between "af-interface default shutdown" and "af-interface default passive" (except it's primary goals ;)) so we need to be accurate with behavior related to Virtual-Template interfaces. Let's look at the firs useful application of "shutdown". It is very handy to use it in OSPF-like interface configuration style to include only required interfaces in routing protocol:

interface Virtual-Template1 type tunnel
 ip ospf 2 area 1

And if our Virtual-Access is connected, OSPF will enable process on this interface also:

R1#sh ip ospf interface b

Virtual-Access1            10.0.1.2        YES unset  up                    up
Virtual-Template1          10.0.1.2        YES unset  up                    down

R1#sh ip ospf interface b
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Vi1          2     1               Unnumbered Lo0     1     P2P   1/1

In this example we are enabling EIGRP only on Virtual-Template1 interface similarly to OSPF:

router eigrp TEST
 !
 address-family ipv4 unicast autonomous-system 1
  !
  af-interface default
   shutdown
  exit-af-interface
  !
  af-interface Virtual-Template1
   no shutdown
  exit-af-interface
  !
  topology base
  exit-af-topology
  network 0.0.0.0
 exit-address-family

But note significant difference. EIGRP will not be enabled on Virtual-Access interface although it is up and running:

R1#sh ip int b
Virtual-Access1            10.0.1.2        YES unset  up                    up
Virtual-Template1          10.0.1.2        YES unset  up                    down 

R1#sh ip eigrp neighbors
EIGRP-IPv4 VR(IPSEC) Address-Family Interfaces for AS(1)
                              Xmit Queue   PeerQ        Mean   Pacing Time   Multicast    Pending
Interface              Peers  Un/Reliable  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Vt1                      0        0/0       0/0           0       6/6            0           0

 Now let's look at "passive-interface default" behaviour:

router eigrp TEST
 !
 address-family ipv4 unicast autonomous-system 1
  !
  af-interface default
   passive-interface
  exit-af-interface
  !
  af-interface Virtual-Template1
   no passive-interface
  exit-af-interface
  !
  topology base
  exit-af-topology
  network 0.0.0.0
 exit-address-family

And as you can see, It is all fine, up and running in such way, just as expected:

R1#sh ip int b
Virtual-Access1            10.0.1.2        YES unset  up                    up
Virtual-Template1          10.0.1.2        YES unset  up                    down

R1#sh ip eigrp neighbors
EIGRP-IPv4 VR(IPSEC) Address-Family Neighbors for AS(1)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
0   10.0.1.1                Vi1                      10 00:00:09  479  2874  0  5

All testing were made with  IOS version 15.2(4)M6. Thank you for interest to this blog post. Please say couple words in comments if it was usefull/interesting, because it seems to me nobody interested in my posts :(