Структура сети (/24):

[LAN_192.168.10.0] -> [e0/0 Router e0/1] -> [e0/0 Catalyst]
[LAN_192.168.10.0] -> [192.168.10.254 Router 192.168.20.254] -> [Vlan1 192.168.20.10 GW 192.168.20.254]

Пинг из сети идет до 192.168.20.254
Пинг с Router идет в любую сторону до конца
Пинг с Catalyst идет только до 192.168.20.254, до 192.168.10.254 пинга уже нет.

Почему?

Настройки по умолчанию, кроме
******************************************
Router:
!
interface Ethernet0/0
ip address 192.168.10.254 255.255.255.0
no mop enabled
!
interface Ethernet0/1
ip address 192.168.20.254 255.255.255.0
!
******************************************
Catalyst:
!
interface Ethernet0/0
duplex auto
!
...
interface Vlan1
ip address 192.168.20.10 255.255.255.0
!
ip default-gateway 192.168.20.254
!
******************************************

Router#show ip route
      192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.10.0/24 is directly connected, Ethernet0/0
L        192.168.10.254/32 is directly connected, Ethernet0/0
      192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.20.0/24 is directly connected, Ethernet0/1
L        192.168.20.254/32 is directly connected, Ethernet0/1

Catalyst#show ip route
      192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.20.0/24 is directly connected, Vlan1
L        192.168.20.10/32 is directly connected, Vlan1