GRE on Cisco routers

From: Hunt Lee (ciscoforme3@yahoo.com.au)
Date: Thu Nov 21 2002 - 10:39:54 GMT-3


I have 2 questions:

1)
                   
                            IPSec
172.16.1.1/24 ----- RTA ============== RTB ------ 172.16.2.1/24
                     | |
              192.168.1.0/24 192.168.2.0/24

Here are more info:-

RTA's Serial0 (connecting to RTB) - 10.64.10.13/27
RTB's Serial1 (connecting back to RTA) - 10.64.10.14/27

Both RTA & RTA are running EIGRP.

As per CCO, IPSec (without GRE) does not transfer routing protocols such as EIGRP /
OSPF etc. I have tested this on the above topology, but I can get the EIGRP routes
across from RTA to RTB & vice versa. What am I missing??

And here are the configs:-

And RTA:-

crypto isakmp policy 15
 hash md5
 authentication pre-share
!
crypto isakmp key 1234a address 10.64.10.14
!
!
crypto ipsec transform-set setOne esp-des esp-md5-hmac
!
crypto map combined local-address Serial1
!
crypto map combined 8 ipsec-isakmp
 set peer 10.64.10.14
 set transform-set setOne
 match address 101
!
!
interface Loopback0
 ip address 192.168.1.1 255.255.255.0
!
!
interface Serial0
 ip address 172.16.1.1 255.255.255.0
 no fair-queue
!
interface Serial1
 ip address 10.64.10.13 255.255.255.224
 no ip route-cache
 no ip mroute-cache
 clockrate 64000
 crypto map combined
!
router eigrp 1
 network 10.0.0.0
 network 172.16.1.0 0.0.0.255
 network 192.168.1.0
 no auto-summary
!
!
access-list 101 permit ip 172.16.1.0 0.0.0.255 172.16.2.0 0.0.0.255

RTB:-

crypto isakmp policy 5
 hash md5
 authentication pre-share
!
!
crypto isakmp key 1234a address 10.64.10.13
!
crypto ipsec transform-set setTwo esp-des esp-md5-hmac
!
crypto map combined local-address Serial0
!
crypto map combined 13 ipsec-isakmp
 set peer 10.64.10.13
 set transform-set setTwo
 match address 101
!
!
interface Loopback0
 ip address 192.168.2.1 255.255.255.0
!
interface Ethernet0
 ip address 172.16.2.1 255.255.255.0
!
interface Serial0
 ip address 10.64.10.14 255.255.255.224
 no fair-queue
 crypto map combined
!
!
router eigrp 1
 network 10.0.0.0
 network 172.16.2.0 0.0.0.255
 network 192.168.2.0
 no auto-summary
 no eigrp log-neighbor-changes
!
!
access-list 101 permit ip 172.16.2.0 0.0.0.255 172.16.1.0 0.0.0.255

*** So instead of getting the EIGRP routes via Tunnel 0 inteface, I'm getting it via
the outgoing interface (serial 0), & the IPSec still works. So what am I missing,
and how does it make a difference if I use GRE over IPSec? I also tested RIPv2 &
getting similar results.

RTA#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

     172.16.0.0/24 is subnetted, 2 subnets
C 172.16.1.0 is directly connected, Serial0
D 172.16.2.0 [90/2195456] via 10.64.10.14, 00:36:16, Serial1
     10.0.0.0/27 is subnetted, 1 subnets
C 10.64.10.0 is directly connected, Serial1
C 192.168.1.0/24 is directly connected, Loopback0
D 192.168.2.0/24 [90/2297856] via 10.64.10.14, 01:24:52, Serial1
RTA#

RTA#sh crypto engine connections act

  ID Interface IP-Address State Algorithm Encrypt Decrypt
   1 Serial1 10.64.10.13 set HMAC_MD5+DES_56_CB 0 0
2000 Serial1 10.64.10.13 set HMAC_MD5+DES_56_CB 0 6
2001 Serial1 10.64.10.13 set HMAC_MD5+DES_56_CB 6 0

RTA#

--

2)

Most configs / examples I found on CCO and books use:

ccrypto ipsec transform-set setTwo esp-des

so when would one use:

ccrypto ipsec transform-set setTwo esp-des <mode transport> ??

Or is it generally not needed / recommended to use the mode transport? If anyone can give me some config e.g., that would be greatly appreciated.

Thanks, HL

http://www.yahoo.promo.com.au/hint/ - Yahoo! Hint Dropper - Avoid getting hideous gifts this Christmas with Yahoo! Hint Dropper!



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