Hello,
The GRE tunnel.
Cisco 2821 [GE0/0] --- Public Internet --- [FE0/0] Cisco 2801
Cisco 2821:
interface Tunnel0
description GRE tunnel to back office
ip address 172.16.0.2 255.255.255.252
ip mtu 1400
ip tcp adjust-mss 1360
tunnel source GigabitEthernet0/0
tunnel destination 94.xxx.xxx.254
!
interface GigabitEthernet0/0
description $Connect-to-upstream-C2901$
ip address 91.xxx.xxx.254 255.255.255.252
ip access-group 101 in
no ip unreachables
ip nat outside
ip virtual-reassembly in
duplex auto
speed auto
!
interface GigabitEthernet0/1
ip address 192.168.102.250 255.255.255.0
ip nat inside
ip virtual-reassembly in
duplex auto
speed auto
!
...
!
ip route 0.0.0.0 0.0.0.0 91.xxx.xxx.253
ip route 192.168.101.0 255.255.255.0 172.16.0.1
!
Cisco 2801:
!
interface Tunnel0
description GRE tunnel to main office
ip address 172.16.0.1 255.255.255.252
ip mtu 1400
ip tcp adjust-mss 1360
tunnel source FastEthernet0/0
tunnel destination 91.xxx.xxx.254
!
interface FastEthernet0/0
ip address 94.xxx.xxx.254 255.255.255.252
ip access-group 101 in
no ip unreachables
ip virtual-reassembly
duplex auto
speed auto
crypto map dynmap
!
interface FastEthernet0/1
ip address 192.168.101.250 255.255.255.0
duplex auto
speed auto
!
...
!
ip route 0.0.0.0 0.0.0.0 94.xxx.xxx.253
ip route 192.168.102.0 255.255.255.0 172.16.0.2
!
show arp from 2801:
2801-voip-gw#sh arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 94.xxx.xxx.253 235 001c.f630.5435 ARPA FastEthernet0/0
Internet 94.xxx.xxx.254 - 0014.1c62.0384 ARPA FastEthernet0/0
Internet 192.168.101.10 3 1c17.d341.135f ARPA FastEthernet0/1
Internet 192.168.101.13 32 0021.5555.3b32 ARPA FastEthernet0/1
Internet 192.168.101.15 17 dc7b.94f8.022a ARPA FastEthernet0/1
Internet 192.168.101.16 6 dc7b.94f8.e6af ARPA FastEthernet0/1
Internet 192.168.101.18 8 001f.9e24.a19c ARPA FastEthernet0/1
Internet 192.168.101.19 21 001e.7ac5.7a82 ARPA FastEthernet0/1
Internet 192.168.101.20 0 001e.7ac5.7a24 ARPA FastEthernet0/1
Internet 192.168.101.21 6 001e.7a26.1fc7 ARPA FastEthernet0/1
Internet 192.168.101.25 36 0021.5554.7ca9 ARPA FastEthernet0/1
Internet 192.168.101.26 23 001f.9eac.dbe7 ARPA FastEthernet0/1
...
Internet 192.168.101.251 1 0015.605f.a46e ARPA FastEthernet0/1
Internet 192.168.101.252 0 0013.21b5.c158 ARPA FastEthernet0/1
ping from 2821:
2821-voip-gw#ping 172.16.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms
2821-voip-gw#ping 192.168.101.250
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.101.250, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms
2821-voip-gw#ping 192.168.101.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.101.10, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/70/72 ms
2821-voip-gw#ping 192.168.101.251
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.101.251, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
ping from 2801:
2801-voip-gw#ping 192.168.101.251
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.101.251, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
As you can see, I can ping some IP addresses on site 2801 but some can't. The same situation if I ping network on site 2821.
show arp from 2821:
2821-voip-gw#sh arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 91.xxx.xxx.253 146 e8b7.48c3.a641 ARPA GigabitEthernet0/0
Internet 91.xxx.xxx.254 - dc7b.94d8.b960 ARPA GigabitEthernet0/0
Internet 192.168.102.10 24 c40a.cbe1.e6e3 ARPA GigabitEthernet0/1
Internet 192.168.102.11 0 001b.38ad.9250 ARPA GigabitEthernet0/1
Internet 192.168.102.12 0 70ca.9b5c.5ec1 ARPA GigabitEthernet0/1
Internet 192.168.102.13 0 ccef.48a2.7a7a ARPA GigabitEthernet0/1
Internet 192.168.102.250 - dc7b.94d8.b961 ARPA GigabitEthernet0/1
ping from 2801:
2801-voip-gw-akvalis#ping 192.168.102.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.102.10, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/7/8 ms
2801-voip-gw-akvalis#ping 192.168.102.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.102.11, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
ping from 2821:
2821-voip-gw-akvalis#ping 192.168.102.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.102.11, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms
Can somebody help to understand why some IPs are seen and some not through GRE tunnel?
