20
ICMP Detection Timeout
Set ICMP detection timeout
3 s
ICMP Detection Retries
Set ICMP detection max. retries
3
Backup Link
Optional dialup/cellular or WAN
Dialup/Cellular
Connection
Backup mode
Optional hot or cold backup
Hot backup
Table 3-2-7-2
Parameters of Link Backup - Backup Mode
Link Backup - Backup Mode
Function description: Select the way of link backup.
Parameters
Description
Hot Backup
Main link and backup Link keep online at the same time.
Cold Backup
Backup line will only be online when the main link is
disconnected.
3.2.8 VRRP
VRRP (Virtual Router Redundancy Protocol) adds a set of routers that can undertake gateway
function into a backup group to form a virtual router. The election mechanism of VRRP will
decide which router to undertake the forwarding task and the host in LAN is only required to
configure the default gateway for the virtual router.
VRRP will bring together a set of routers in LAN. It consists of multiple routers and is similar to a
virtual router in respect of function. According to the VLAN interface IP of different network
segments, it can be virtualized into multiple virtual routers. Each virtual router has an ID number
and up to 255 can be virtualized.
VRRP has the following characteristics:
Virtual router has an IP address, known as the Virtual IP address. For the host in
LAN, it is only required to know the IP address of virtual router, and set it as the
address of the next hop of the default route.
Host in the network communicates with the external network through this virtual
router.
A router will be selected from the set of routers based on priority to undertake the
gateway function. Other routers will be used as backup routers to perform the
duties of gateway for the gateway router in case of fault of gateway router, thus to
guarantee uninterrupted communication between the host and external network
