The ATEN UE3310 USB3.1 Gen1 Extender Cable allows users to extend the distance between the computer and USB devices up to 10 m (33 ft). The UE3310 is a high-quality, cost-effective solution for professional environments such as hospitals, factories and business facilities.
Course Of The Month
9 days, left to enrollBecome a Premium Member and unlock a new, free course in leading technologies each month.
Solved
GLBP with NAT query
Posted on 2010-11-21
Hi guys,
We have a few sites which use host-dependent GLBP to load balance traffic over two links, these sites are usually 'tails' and have NAT configured on them for clients, etc.
Now for some of these sites, the links are unequal cost, i.e. one could be a 40/40 fiber and the other an old ADSL1 link. Many times traffic, such as voice goes through the slower link, and if the link is congested - it affects voice quality and frequent dropouts.
I changed GLBP to weighted, with ratios of 1:5 and that seems to have improved things. However I have noted the following statement on some sites:
"Host dependent load balancing will need to be used when using stateful Network Address Translation (NAT) because it requires each host to be returned the same virtual MAC address each time it sends an ARP request for the virtual IP address
What this means is that Host-dependent ensures a host uses one and only one gateway for its traffic. In case of round-robin/weighted, a host sends some packets through 1st gateway and some packets of the same session to the 2nd gateway and this doesn’t work well with NAT"
Now I know the default ARP timeout for Cisco is 4 hours. Not all our switches are cisco, however would having weighted GLBP affect windows based clients ? I haven't had any noise from the sites where I changed the configs, but just need to know in case it might be causing minor disruptions.
Cheers,
We have a few sites which use host-dependent GLBP to load balance traffic over two links, these sites are usually 'tails' and have NAT configured on them for clients, etc.
Now for some of these sites, the links are unequal cost, i.e. one could be a 40/40 fiber and the other an old ADSL1 link. Many times traffic, such as voice goes through the slower link, and if the link is congested - it affects voice quality and frequent dropouts.
I changed GLBP to weighted, with ratios of 1:5 and that seems to have improved things. However I have noted the following statement on some sites:
"Host dependent load balancing will need to be used when using stateful Network Address Translation (NAT) because it requires each host to be returned the same virtual MAC address each time it sends an ARP request for the virtual IP address
What this means is that Host-dependent ensures a host uses one and only one gateway for its traffic. In case of round-robin/weighted, a host sends some packets through 1st gateway and some packets of the same session to the 2nd gateway and this doesn’t work well with NAT"
Now I know the default ARP timeout for Cisco is 4 hours. Not all our switches are cisco, however would having weighted GLBP affect windows based clients ? I haven't had any noise from the sites where I changed the configs, but just need to know in case it might be causing minor disruptions.
Cheers,
[X]
Welcome to Experts Exchange
Add your voice to the tech community where 5M+ people just like you are talking about what matters.
- Help others & share knowledge
- Earn cash & points
- Learn & ask questions
2 Comments
I dont think your definition of weighted GLBP is correct.. a client will not send some packets one way and some the other, as the client only cares about where the next hop comes from (this is why GLBP is not 100% true load balancing)
Let say we have a 8/2 weight on 2 GLBP routers.. the AVG will issue the mac address of the first router for the first 8 requests, then issue the mac for the second router for the following 2, that another 8 to the first router again.
So, so long as the clients maintain a connection their ARP cache will not time-out and you shouldnt run into problems.
You may also want to throw some QoS on your VOIP, or at least a second GLBP group for VOIP traffic.
Hope this helps
J
Let say we have a 8/2 weight on 2 GLBP routers.. the AVG will issue the mac address of the first router for the first 8 requests, then issue the mac for the second router for the following 2, that another 8 to the first router again.
So, so long as the clients maintain a connection their ARP cache will not time-out and you shouldnt run into problems.
You may also want to throw some QoS on your VOIP, or at least a second GLBP group for VOIP traffic.
Hope this helps
J
Featured Post
Question has a verified solution.
If you are experiencing a similar issue, please ask a related question
I recently attended Cisco Live! in Las Vegas, a conference that boasted over 28,000 techies in attendance, and a week of hands-on learning hosted by a solid partner with which Concerto goes to market. Every year, Cisco displays cutting-edge technol…
Shadow IT is coming out of the shadows as more businesses are choosing cloud-based applications. It is now a multi-cloud world for most organizations. Simultaneously, most businesses have yet to consolidate with one cloud provider or define an offic…
Viewers will learn how to properly install and use Secure Shell (SSH) to work on projects or homework remotely.
Download Secure Shell:
Follow basic installation instructions:
Open Secure Shell and use "Quick Connect" to enter credentials includi…
In this brief tutorial Pawel from AdRem Software explains how you can quickly find out which services are running on your network, or what are the IP addresses of servers responsible for each service. Software used is freeware NetCrunch Tools (https…
Suggested Courses
Earn Certification
HTML5 Specialist - Certification
Free withPremium
Course of the Month9 days, left to enroll
617 members asked questions and received personalized solutions in the past 7 days.
Join the community of 500,000 technology professionals and ask your questions.