19 votes

How does gratuitous ARP work?

A Gratuitous ARP is an ARP Response that was not prompted by an ARP Request. The Gratuitous ARP is sent as a broadcast frame, as a way for a node to announce or update its IP to MAC mapping to the ...
Eddie's user avatar
  • 15k
8 votes
Accepted

Strange router's MAC address from ICMP Echo Reply?

You are confused. What you claim is your router's MAC address is not your router's MAC address. The MAC address is in the range, 0000.0C07.ACxx, which is the MAC address range for HSRP. The 06 on the ...
Ron Maupin's user avatar
  • 99.6k
6 votes
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Cisco HSRP CAM vs ARP timeout

What the ISP means is that as they make changes, you may lose connectivity for a time because the ARP table entries your router has with them will not match the changes it is making. If you reduce the ...
Ron Maupin's user avatar
  • 99.6k
6 votes
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HSRP change priority didn't failover

You forgot to use the standby 5 preempt command. It is also a good idea to set a preempt delay. Hot Standby Router Protocol (HSRP): Frequently Asked Questions: Q. Which HSRP router requires that I ...
Ron Maupin's user avatar
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6 votes
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HSRP on Distribution Layer L3 Switches

You'll need to make sure that both SVI10s of Dist1 and Dist2 can hear each other's HSRP hello packets. HSRP active/standby negotiation cannot complete without that. Possibly, VLAN 10's spanning tree ...
Marc 'netztier' Luethi's user avatar
5 votes
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Breaking a stack switches (with SVIs as gateway) - using HSRP

You will need HSRP or VRRP for you FHRP if you want redundancy for your gateway. Each switch will need an SVI for each VLAN, and each VLAN will have its own FHRP group. You place the group for a VLAN ...
Ron Maupin's user avatar
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5 votes
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How to change HSRP version 1 to 2 without downtime?

I can't think of a way to achieve this within the limits of "same set of router interfaces of the same pair/group of routers". HSRPv1 and v2 are: a) incompatible and b) mutually exclusive on one ...
Marc 'netztier' Luethi's user avatar
5 votes
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How exactly does a router get elected as an Active router in HSRP?

Cisco has many documents to explain such things. For example, Hot Standby Router Protocol (HSRP): Frequently Asked Questions: Q. If there is no priority configured for a standby group, what ...
Ron Maupin's user avatar
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4 votes
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How to resolve a spanning tree issue on a server trunk port?

Solved This command was missing in e1/27 interface. spanning-tree port type edge trunk Full interface output look like following. interface Ethernet1/27 description Connected to server switchport ...
Satish's user avatar
  • 4,379
4 votes
Accepted

Connecting an SRX chassis cluster to redundant upstream WAN links

If I put two interfaces (one on each SRX) in a reth, is that sufficient to ensure that there won't be any loops? Yes* - reth interfaces are essentially a logical L3 interface - they will not loop ...
Benjamin Dale's user avatar
4 votes
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HSRP Tracking an Ip

For R2 to become the active HSRP router, the priority has to be higher than R1. You've set the priority on R1 to 150, and the decrement value in the track statement to 20. So when the IPSLA "fails" ...
Ron Trunk's user avatar
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4 votes
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HSRP on multilayer switch not working

Looking at the config have you created the vlans? I can see the vlan interfaces configured but the running-config doesnt show any vlan config that would create the vlan. show vlan brief and see if the ...
The Footsie's user avatar
4 votes
Accepted

HSRP switching active state but destination is unreachable

After isolating the issue to group 5 and group 6 not activating on the failover router by tracerouting towards my destination as the comments suggested. I managed to solve it by tracking interface fa0/...
Eslam Allam's user avatar
3 votes
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VRRP vs HSRP for load sharing

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 ...
Ron Maupin's user avatar
  • 99.6k
3 votes

Router Ethernet port ip no accessible from clients

Problem1: You should have consistent ospf cost, the L3 routing is independent of the L2 hsrp gateway redundancy Problem1b: You host vlans hanging off the Nexus devices should be passive for OSPF, why ...
Pieter's user avatar
  • 1,427
3 votes
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Multiple HSRP group on same VLAN interface

As long as the VIP i in the same subnet as the secondary address(s), This should work. You can verify it by typing show hsrp If the VIP is active, it should be working.
Ron Trunk's user avatar
  • 67.5k
3 votes

HSRP limitations on Catalyst 3560

An HSRP group on an interface is an instance. Each layer-3 interface could have an HSRP group 1, but each is a different instance, and, indeed, are actually different HSRP groups, despite having the ...
Ron Maupin's user avatar
  • 99.6k
3 votes

Is it possible to make a truly active\active L3 VRRP\HSRP configuration between two Nexus in a vPC

You actually don't have to do anything. VPC paired Nexus work exactly as you want them to. The prerequisite is that all systems involved (i.e. the servers) are attached to the Nexus over a VPC ...
Marc 'netztier' Luethi's user avatar
3 votes

HSRP on Distribution Layer L3 Switches

HSRP requires L2 connectivity between the backing routers. So, a L3 link between dist 1 and 2 produces the problem you see. Cisco's linked guideline states (emphasis mine): Additionally, in a less ...
Zac67's user avatar
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3 votes
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HSRP and DHCP problem

You haven't mentioned the equipment in use and you have not said clearly that the layer 3 switch is acting as the DHCP server but you seem to indicate that is the case. I can be pretty sure that in ...
FrameHowitzer's user avatar
2 votes

What are the differences between VRRP and HSRP?

HSRP : 1) CISCO Proprietary 2) RFC 2281 3) Multicast group Ip: 224.0.0.2 V1 224.0.0.102 V2 4) Port No. UDP 1985 5) PREEMPT: By default disabled 6) Virtual Mac address: 0000.0c07.acxx ...
Kashyap Mehta's user avatar
2 votes
Accepted

Regarding traffic blackholing in case of vpc and hsrp

I'll answer Q2 first: Suppose a PC in VLAN 100 sends a packet to a PC in VLAN 200. Let's say the packet takes the VPC link to 7K2. Since the active SVI is on 7K1, the packet is forwarded across ...
Ron Trunk's user avatar
  • 67.5k
2 votes

change around 100 hsrp groups priority

Why would you need filters to begin with? It is standby X priority P in Cisco IOS. Copy all the interface config into you favorite editor, and replace priority P with priority P'. Then just paste ...
ar_'s user avatar
  • 1,133
2 votes

WAN project requirements increasing

The design seems pretty straightforward to me, with one apparent oddity I'd like to know more about: Is there a particular reason not to hook up SITE5 to the WAN directly, but across Site 1 ? ...
Marc 'netztier' Luethi's user avatar
2 votes
Accepted

HSRP vs VRRP interface tracking

Object tracking for any service that uses enhanced object tracking is the same. HSRP, VRRP and GLBP all use enhanced object tracking in the same way. The original HSRP tracking simply tracked the ...
Ron Maupin's user avatar
  • 99.6k
2 votes
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HSRP - 2 separate Virtual Router for Distribution and WAN?

What you would do is configure a virtual router for each VLAN. Configure HSRP on The SVIs on your core switches. A host will use the virtual router as the gateway for the VLAN to which it is connected....
Ron Maupin's user avatar
  • 99.6k
2 votes
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vPC with HSRP strange arp issue

Resolution: Problem was host were running on round-robin bonding configuration which cause lots of MAC flapping and that cause lockup MAC table and preventing new MAC entires. We re-configured all ...
Satish's user avatar
  • 4,379

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