eng_ahmedaseng_ahmedas Member Posts: 69 ■■□□□□□□□□
Dear Friends
I wish u r all in very good health ...... while i was studying HSRP, i see the following command "standby 1 preempt delay" ...... and that was its description in the cisco material

"When a preempting distribution switch is rebooted, HSRP preempt communication should not begin until the distribution switch has established full connectivity to the rest of the network. This allows routing protocol convergence to occur more quickly once the preferred router is in an active state. To accomplish this, measure the system boot time and set the HSRP preempt delay to a value 50 percent greater than the boot time. This ensures that the primary distribution switch establishes full connectivity to the network before HSRP communication occurs."

i couldn't understand it well ... can anyone explain in more detail ..... please

thanks in advance


  • EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    Preempt is used if you want the layer 3 switch/router with the highest priority to become Active at all times, so if a switch/router with the highest priority comes online it will preempt the current Active viirtual router and become Active itself.
    Now imagine a router comes online and due to a higher priority it becomes the hsrp Active, all devices on the local segment will use this router as the default gateway.The two routers participating in HSRP are BGP edge routers, these router may take a couple of minutes to establish neighbor adjacencies and learn routing tables, what do you think will happen to the devices that are using the newly Active HRSP router as their default gateway? They will be isolated at layer 3, wouldn't it be nicer to delay this router from becoming HRSP Active until the bgp adjacencies are established?
    So by setting a delay to 1.5 * boot time you are ensuriing the router has enough time to boot and learn its appropriate layer 3 info.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
  • eng_ahmedaseng_ahmedas Member Posts: 69 ■■□□□□□□□□
    Thanks tooooo much dear EdTheLad , you help me tooo much

    Thanks again
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