Redundancy includes:
1) Modules
2) Links
3) Devices
Between two core switches:
1) Trunk
2) VTP
3) STP
4) HSRP/VRRP/IRDP/GLBP
Supervisors redundancy can only acts as a backup role, you can't run LB on it.
RPR(Router Processor Redundancy)
1) switchover 2~4 mins
2) MSFC(Multilayer Switching Feature Card) & PFC (Policy feature card) booted but not functional
RPR plus(RPR+)
1) switchover 30~60 secs
2) MSFC & PFC booted and operational.
SRM with SSO(Stateful SwitchOver)
NSF with SSO
configurations:
1) switch(config)# redundancy
2) switch(config-red)# mode rpr-plus
3) switch# show redundancy status
Serial interface dont support arp
when a pc is not configured with an ip address for the gateway, you can use proxy-arp to get to the remote network.
arp packets are broadcasted.
proxy-arp is enabled on all ethernet interface on cisco routers by default.
1) checking route table
2) reply arp request
when using proxy-arp
if the connected link is down, it takes arp-cache update time out to recover
4 hours by default on cisco routers.
if the upper link goes down, it takes the routing protocol conver time to recover.