Switching

hi

1:what is GRES and NSR in VC

2:I see part of GRES is sync pfe table to backup member,if it works in this way ,why we need NSR,

when switchover happens,new master member has PFE table to forward packets

3:commit sync

 when work on VC,we need to use this commit sync everytime to commit config,right?

if not,config will only be submitted in master RE,right?

thanks in advance

1- You can examine http://www.juniper.net/techpubs/en_US/junos9.5/information-products/topic-collections/swconfig-high-availability/gres-overview.html and http://www.juniper.net/techpubs/en_US/junos9.5/information-products/topic-collections/swconfig-high-availability/nsr-overview.html about your request.

2- if you use dynamic routing protocols like BGP and if you want to change  routing engine switch over anytime , you can see BGP session does not down.

3- if you want to use same config with dual routing. it must be commit synchronize

commit synchronize is a must in VC,right?

I want to know the real benbifit of NSR ....

if you can read that ( http://www.juniper.net/techpubs/en_US/junos9.5/information-products/topic-collections/swconfig-high-availability/nsr-overview.html ), you can understand

NSR Keeps the rpd running on the Backup RE thereby mainting the adjacencies

GRES allows routing platforms with redundant REs to continue forwarding packets, if one RE fails. GRES preserves interface and kernel information to ensure that traffic forwarding is not interrupted when the mastership change. (Remember the Control plane is seperated for the Forwarding/Data plane). GRES DOES NOT preserve the control plane, which means the routing protocol process (rpd) must be restarted and the information learned through that process must be relearned. Since both RE's have their own rpd, then the rpd on the backup RE, now transitioning into the Master, must be started. This is where NSR comes in and can only be configured when you have GRES enabled.To preserve routing during a switchover, you enable NSR. NSR Keeps the rpd running on the Backup RE thereby mainting the adjacencies. then your next question is why isn't this feature enabled by default? Power and Control.
You do not need to run the command commit sync each time. You can use the command "set system commit synchronize" so it is done automatically

thank u

my next question is: what is the benfit of this NSR for packet forwarding

with PFE table,it can work,if rpd need start,just let it restart,no impact to traffic

for commit sync,i tried change one config in syslog,and commit,checked config in master and backup member,no difference

not sure how to verify this commit sync is different from commit

Hi Robert,

 If I recall correct, EX defaults to commit synchronize in case you have a VC set up. That is different from other JUNOS platforms (like M, MX, T etc.).

 I'm not 100% sure about the EX, but in M/MX/T series, JUNOS will force you to configure system commit synrhonize as soon as you configure nonstop-routing.

 Cheers,

Hey Ricardo,

 For packet forwarding, NSR could help you for your incoming traffic.

 Imagine an eBGP peer of yours, for instance. When you have GRES enabled on your end, it's true that your forwarding won't be impacted during a RE switchover, but your protocols will restart. Until they re-converge, this change is most likely to trigger an action on your neighbor, like a path change for your prefixes, thus sending packets via another link that it has.

 With NSR, since your supported protocol adjacencies will remain intact, the RE switchover on your end will be purely seamless. As far as your eBGP neighbor is concerned, nothing happened.

 Cheers,

hello,erdems

1:yes,it seems in EX VC,commit will sync to backup member,no need  command "commit sync"

2:still confused by this NSR

I know it will run rpd in backup node ,keep adjency stats

but what is the benfit,when I switchover to backup,packets is forwarder out via PFE table,even routing protocol restart in the new master,it doesn't metter

would u like to give me a detail and real example for NSR which will improve the packet forwarding

thanks in advance

Hey Robert,

 I hope I already did 🙂

 Please see my previous replies and let me know whether it's clear.

 Cheers,