I have one router 3725 connected with two switches 3560 ,switches connected between itch other,net works under OSPF. On router I have few sub-interfaces F0/0.1 (server 1), F0/0.2 (...) ,F0/1.1 (server 2). When one link between router and switch crashes,switch with crashed link cat rich router throe another switch.Its all work fine?,but I cant understand what the problem with sub-interfaces on the router,when link crashed the status of interface/sub-interfaces is "Ethernet is up,line protocol is down" and all sub-int on this F0/. link become unrichible. How I can backup this?
The sub-interfaces are logical interfaces and rely on the physical main interface. If you have a physical connection to a switch and the switch dies, the main interfaces and its sub-interfaces will be down.
If you want redundancy, you need another physical main interface (another port in the router) connected to a separate switch.
I have seen two solutions (stated on this forum) to support one router with two ethernet interfaces on one network:
1) Backup interface. Cisco allows you to have two interfaces (or sub interfaces for vlans) on the same router with the same IP config, as long as you use the "backup interface" command. This uses ONE interface at a time and does not lose performance and should not cause any problems. This is mostly a hardware backup of the interface (uses linktest keepalive). If your good equipment is on the backup network and the router did not switch then you are disconnected.
2) Bridge interface. You can configure BVI as your main IP interface and then setup the physical interface (or sub interfaces) into a bridge group. This uses both interfaces and ethernet STP to find the best path. Performance can be very bad with IRB and may also cause other strange problems due to unexpected bridging. This is mostly a software backup of the interface (uses STP for best path). There is no primary/backup interface so both should work and may pass traffic between the two networks if there is no other path (and kill the CPU on our router).
Note: Cisco access points use bridging between radios and ethernets, so IRB is in use every day by IOS....
Remember your subinterfaces (VLANS) are using the main physical interface, so it's all or nothing on that interface.
There is no good simple choice....use two routers and HSRP/VRRP and dynamic routing....
Cisco needs to make "backup interface" more of a bridge interface without the performance loss.
I have 2 routers that had multiple sub interfaces on each router. EG
You can specify HSRP on each of the sub interfaces, and have a HSRP address for each sub interface. You do this the same as you would HSRP for a normal interface.
This obviously means that you need 2 routers. Otherwise you can do the same with a second interface on the same router, and have sub interfaces of that but if the router dies then you'll lose everything. HSRP is the better way to go i'd suggest.
Question We run asr9001 with XR 6.1.3, and we have a very long delay to
login w/ SSH 1 or 2 to the device compare to IOS device. After
investigation, the there is 1s delay between the client KEXDH_INIT and
the server (XR) KEXDH_REPLY. After debug ssh serv...
Introduction The purpose of this document is to demonstrate the Open
Shortest Path First (OSPF) behavior when the V-bit (Virtual-link bit) is
present in a non-backbone area. The V-bit is signaled in Type-1 LSA only
if the router is the endpoint of one or ...
Hi, I am seeing quite a few issues with patch install and wanted to
share my experience and workaround to this. Login to admin via CLI, then
access root with the “shell” command Issue “df –h” and you’ll probably
see the following directory full or nearly ...