Compare two configurations line by line, with a pass that flags changes likely to drop traffic.
Heuristic, vendor-agnostic. A review aid, not a substitute for reading the diff.
no shutdownA 'no shutdown' was removed — the interface may go administratively down.
mtu 9000MTU changed — mismatched MTU breaks OSPF adjacency and causes black-holing.
shutdownAn interface is being shut down.
permit icmp any any echo-replyA permit rule was removed — traffic that was allowed will now be denied.
ip route 0.0.0.0 0.0.0.0 203.0.113.1A static route was removed — the destination may become unreachable.
| 1 | 1 | hostname edge-01 | |
| 2 | 2 | ! | |
| 3 | 3 | interface GigabitEthernet0/0 | |
| 4 | 4 | description WAN | |
| 5 | 5 | ip address 203.0.113.2 255.255.255.0 | |
| 6 | 6 | ip access-group WAN_IN in | |
| 7 | 7 | no shutdown | |
| 8 | 8 | ! | |
| 9 | 9 | interface GigabitEthernet0/1 | |
| 10 | 10 | description LAN | |
| 11 | 11 | ip address 10.20.0.1 255.255.255.0 | |
| 12 | − | no shutdown | |
| 12 | + | mtu 9000 | |
| 13 | + | shutdown | |
| 13 | 14 | ! | |
| 14 | 15 | ip access-list extended WAN_IN | |
| 15 | 16 | permit tcp any any established | |
| 16 | − | permit icmp any any echo-reply | |
| 17 | 17 | deny ip any any log | |
| 18 | 18 | ! | |
| 19 | − | ip route 0.0.0.0 0.0.0.0 203.0.113.1 | |
| 19 | + | ip route 0.0.0.0 0.0.0.0 203.0.113.254 |