eigrp classless...

even with auto summary on...

eigrp can act classlessly with auto-summary on with a directly connected neighbor, bordering another major classful network... of course we knew this, just probably haven't thought of this behavior in a while...

the 10.1.1 subnet will be advertised intact to the border router r2... r3 will receive the 10.1.1 network as a summary... see below... all routers have auto-summary turned on...

R1#sh run | b eigrp
router eigrp 1
 network 10.0.0.0
 auto-summary

R1#sh ip route | b Gate
Gateway of last resort is not set

      3.0.0.0/8 is subnetted, 1 subnets
D        3.0.0.0 [90/2809856] via 10.1.2.2, 00:12:33, Serial1/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.1.1.0/24 is directly connected, Loopback0
L        10.1.1.1/32 is directly connected, Loopback0
C        10.1.2.0/24 is directly connected, Serial1/0
L        10.1.2.1/32 is directly connected, Serial1/0
D     192.168.1.0/24 [90/2681856] via 10.1.2.2, 00:13:01, Serial1/0

R2#sh ip route | b Gate
Gateway of last resort is not set

D     3.0.0.0/8 [90/2297856] via 192.168.1.3, 00:13:35, Serial1/1
      10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
D        10.0.0.0/8 is a summary, 00:12:50, Null0
D        10.1.1.0/24 [90/2297856] via 10.1.2.1, 00:15:03, Serial1/0
C        10.1.2.0/24 is directly connected, Serial1/0
L        10.1.2.2/32 is directly connected, Serial1/0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Serial1/1
L        192.168.1.2/32 is directly connected, Serial1/1

R3#sh ip route | b Gate
Gateway of last resort is not set

      3.0.0.0/8 is variably subnetted, 3 subnets, 3 masks
D        3.0.0.0/8 is a summary, 00:15:11, Null0
C        3.3.3.0/24 is directly connected, Loopback0
L        3.3.3.3/32 is directly connected, Loopback0
D     10.0.0.0/8 [90/2681856] via 192.168.1.2, 00:14:26, Serial1/1
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Serial1/1
L        192.168.1.3/32 is directly connected, Serial1/1

note r3's loopback 3.3.3.3... because it belongs to a different major class, it is only ever advertised as a summary...  of course none of this matters with no auto-summary...

R2#sh ip route | b Gate
Gateway of last resort is not set

      3.0.0.0/24 is subnetted, 1 subnets
D        3.3.3.0 [90/2297856] via 192.168.1.3, 00:03:31, Serial1/1
      10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
D        10.1.1.0/24 [90/2297856] via 10.1.2.1, 00:23:53, Serial1/0
C        10.1.2.0/24 is directly connected, Serial1/0
L        10.1.2.2/32 is directly connected, Serial1/0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Serial1/1
L        192.168.1.2/32 is directly connected, Serial1/1

however it is important to note that no auto-summary does a fine job behaving classlessly without the extra effort of a wildcard mask... 

R3#sh run | b eigrp
router eigrp 1
 network 3.0.0.0
 network 192.168.1.0