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  1. Do both VRRP and HSRP support load sharing across more than one virtual routers based on the grop number ?

  2. In using VLAN's does the group number (in load balancing) will remain same in case of both HSRP and VRRP ?

  3. So, at a time I can use both, VLAN (same group number)as well as virtual router(diff group number) as a load balancer in either HSRP or VRRP ? Is there any limit as to how many load balancing a router can handle ex. if there are lots of VLANs , I need load balancer for them as well as for different group number ( say 100 , 200) apart from the VLANs group (which can be say 300) ?

Is my understanding correct here ?

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer. – Ron Maupin Feb 19 '18 at 20:03
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FHRPs, like VRRP, and HSRP, don't load balance anything; that is not their purpose. The purpose of an FHRP is to give a virtual gateway, which can fail to a different physical router in the case of a primary router failure. The gateway is either statically configured on hosts, or assigned to the hosts by DHCP. Some people will also use the assigned gateway to try to spread the traffic load across multiple routers, but that can be done with or without an FHRP. That is simply an artifact of which hosts are assigned which gateway.

For example, if you have two routers and two VLANs, you can assign the hosts on VLAN 1 to use Router 1 as their gateway, and the hosts on VLAN 2 to use Router 2 as their gateway. That spreads the traffic load, but it does nothing for a failure situation.

What the FHRP will do for you is create virtual router addresses. In that case, the Virtual 1 could use Router 1 as its primary router, and Virtual 2 could use Router 2 as its primary router. That would be, under normal circumstances, no different than simply using the two routers without an FHRP. What it gives you is the ability for all the traffic to use one of the routers if the other router fails.

Some people take this even farther, and they assign multiple FHRP groups on the router interfaces. In such a case VLAN 1 could have two virtual router addresses on the single VLAN, and one of the virtual addresses could use Router 1 as its primary router, and the other virtual address could use Router 2 as it primary router. Some hosts would then be assigned to one virtual address as their gateway, and the other hosts would be assigned to the other virtual address as their gateway. This is what many people call load balancing, even though it is not really load balancing, and it has problems, especially if STP directs the frames to the root bridge, which then has to send them another direction to get to the router, resulting in sub-optimal traffic flow.

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  1. With a single group, they only provide resilience, the active router will service all traffic for the group, you are correct that you would need multiple groups to achieve crude load-balancing (although this is not a good solution), each group would have its own virtual IP to provide load-balancing, one router would be active for one group, and the other active for the other group, you would then have to make sure that half the hosts on the LAN had one of the virtual IPs as their default gateway and the other half had the other virtual IP. GLBP (Gateway Load Balancing Protocol) was designed to provide first-hop resilience and load-balancing. GLBP responds with multiple virtual MACs when hosts ARP for the GLBP virtual IP, some hosts receive one MAC, others received the other MAC, one router services one MAC and the other router services the other MAC. If one router goes down, the other router services both MACs.

  2. Not sure what you are asking, but you can use the same group number on multiple VLANs as the HSRP/VRRP traffic of different VLANs will never interact. There are situations where it would be better to use unique group number such as if you plan on using Q-in-Q in the future.

  3. Not sure what you mean, you can use either the same group number on multiple VLANs or different group numbers, or a combination of both. There will be a platform limit to how many total groups (across all VLANs) that the switch can support. HSRP/VRRP are not load balancing protocols though, use GLBP instead

  • My terms might not be precise so if you get a gist of it, it's good enough. I edited my question, hope you understand . – Anshul Choudhary Nov 11 '17 at 21:32

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