I am trying to workout why a router swap at my HQ out is causing me so many problems.
I have an Ethernet network of which the default gateway in 10.0.0.1 /8. To this I introduced 2 x new Cisco routers, 10.0.0.2 & 10.0.0.3
The default gateway, a Cisco 3640, has a small number of static routes these are:0.0.0.0 pointing to a PIX (10.0.0.99). 172.22.0.0 /24 pointing at another router 10.0.0.5 172.16.0.0 /16 pointing to another router 10.0.0.6
The PIX terminates some remote VPN's with LAN IP's 192.168.X.X /24.
All I did was move the default gateway address to the 2 x new Cisco routers (using HSRP) & renumber the 3640 with a new IP address 10.0.0.4. I replicated the static routes off the 3640 on the 2 x new Cisco routers. I can ping from a remote site to my Head Office E-Mail Server & Intranet Server but I cannot access the E-Mail itself, nor HTTP to the Intranet server.
The 3640 and 2 x new Cisco routers don't route any traffic over the WAN. They simply route on the Ethernet segment to either the PIX or next hop routers.
I guess that the old 3640 router probably sent IP redirects to the LAN hosts as the HQ Servers using a 'route print' seem to have learnt the PIX / other router addresses as their next hop.
But why oh why do some of the applications stop to work when I swap the10.0.0.1 gateway IP to my new boxes ?
When I reversed the change everything started to work again.3640 Ethernet Config:
interface FastEthernet0/0 ip address 10.0.0.1 255.0.0.0 (IP address changed to 10.0.0.4 after migration) speed auto half-duplex
New Router 1 (Cisco 2801)
Fa0/0 (after moving default gateway address over)
interface FastEthernet0/0 ip address 10.0.0.2 255.0.0.0 no ip redirects speed auto duplex auto standby 1 ip 10.0.0.1 standby 1 priority 105 standby 1 preempt
New Router 2 (878)
interface vlan 1 ip address 10.0.0.3 255.0.0.0 no ip redirects speed auto duplex auto standby 1 ip 10.0.0.1 standby 1 preempt