GRE tunnel performance issue- How to properly check the Internet underlay health

[Nitin Nayar]

Hi Guys,

I have set up a GRE tunnel between branch office router and ZScaler. When browsing the internet from the branch office through the tunnel I am having intermittent performance issues during certain times of day.

I have checked the usual suspects like MTU etc... and that looks good.

Zscaler is saying that might be due to Internet congestion. I am looking to set up tests from my router to Zscaler tower and want to emulate GRE traffic path as closely as possible.

The Cisco routers give me the option to set up TCP / ICMP pings to the Zscaler GRE tunnel destinations. Which one is closest to the traffic path taken by GRE packets?

Any other way I can create a GRE-type packet (not sure if Zscaler will respond to it)

Appreciate any advice

[Georg Pauwen]

Hello,

use an extended ping on your router and specify the tunnel as the source.

That said, can you post the configuration of the router ?

[Nitin Nayar]

Hi Georg,

I have done that and am able to ping through the GRE Tunnel.

I also want to ping the GRE Tunnel VIP (Public IP) provided by ZScaler to measure the loss / latency outside the GRE tunnel. I can do a ICMP / TCP ping to the GRE Tunnel VIP (Public IP) provided by ZScaler, but looking for guidance on what is recommended as I can do a PING with protocol type 47.

Any ideas?

[Georg Pauwen]

Hello,

just to be sure I understand: you want to measure performance OUTSIDE of the tunnel ?

You could temporarily route all traffic to the public IP address of ZScaler instead of through the tunnel. Post the configuration of your router, that will make it easier to determine how that can be accomplished...