Verifying the GRM network

Testing connectivity to the back-end DNS nameserver

If you are deploying a GRM DNS server, you must verify connectivity to the back-end DNS nameserver after you assign an authoritative DNS nameserver's IP address to the GRM server.

At a remote console, enter the following command to initiate a zone transfer:

dig axfr domain @server

If the zone transfer is successful, the back-end DNS nameserver is receiving requests proxied to it by the GRM server.

Verifying that center and edge caches are reporting in

After configuring the GRM options, you must verify that all center and edge caches are reporting in to the GRM server. To verify that all center and edge caches are reporting in, view the GRM server access log in the Appliance Manager. The GRM server access log lists all the center and edge caches and reports whether they are reporting their status to the GRM server.

To view the GRM server access log from the Appliance Manager, select Data tab > GRM Server > Caches.

If center or edge caches are not reporting in, see Troubleshooting GRM configuration issues.

Verifying edge group redirection for a GRM DNS server

For a GRM DNS server, to verify that CDN clients in an edge group are directed to an edge cache assigned to that edge group, complete the following steps.

Step	Action
1	Use the `telnet` command to access a client within the edge group.
2	Enter the following command: nslookup After you enter the preceding command, the `nslookup` prompt is displayed. For example: `>`
3	Force the client to use the GRM DNS server as its local DNS nameserver by entering the following at the nslookup prompt: > `server grm_ip_address`
4	At the `nslookup` prompt, initiate a DNS lookup to a domain controlled by the GRM DNS server. For example: > `images.cdn.company.com` The IP address of each edge cache returned by the GRM DNS server is displayed.
5	Verify that the IP addresses displayed at the `nslookup` prompt are for edge caches assigned to the correct edge group.
6	Examine the `x-grm-method` field in the GRM server access log to determine why the GRM DNS server returned each edge cache. See Using the GRM server access log for test verification for information about accessing and using the GRM server access log. If the IP addresses returned by the GRM DNS server are not the IP addresses that you expected, see Troubleshooting GRM configuration issues for troubleshooting information.
7	Return to the `nslookup` session, exit `nslookup`, and restart it. Exiting `nslookup` causes the client to revert to its local DNS nameserver.
8	Repeat Steps 4 and 5.
9	Examine the GRM server access log to verify that the IP address of the local DNS nameserver matches the IP address listed for the DNS lookup in Step 4. If the IP address returned by the GRM DNS server does not match or if edge caches were not returned, see Troubleshooting GRM configuration issues for troubleshooting information.

Verifying edge group redirection for a GRM L7 server

For a GRM L7 server, to verify that CDN clients in an edge group are directed to an edge cache assigned to that edge group, complete the following step.

Step

Action

Examine the x-grm-method field in the GRM server access log to determine why the GRM L7 server returned each edge cache.

See Using the GRM server access log for test verification for information about accessing and using the GRM server access log.

If the IP addresses returned by the GRM L7 server are not the IP addresses that you expected, see Troubleshooting GRM configuration issues for troubleshooting information.

Verifying GRM redirection for clients outside of edge groups for a GRM DNS server

For a GRM DNS server, to verify that clients not associated with edge groups are directed to the closest center caches, complete the following steps.

Step	Action
1	Use the `telnet` command to access a client that is not part of an edge group.
2	Enter the following command: nslookup After you enter the preceding command, the `nslookup` prompt is displayed. For example: `>`
3	Force the client to use the GRM DNS server as its local DNS nameserver by entering the following at the `nslookup` prompt: > server grm_ip_address
4	At the `nslookup` prompt, initiate a DNS lookup to a domain controlled by the GRM DNS server. For example: > images.cdn.company.com The IP address of each center cache returned by the GRM DNS server is displayed.
5	Verify that the IP addresses displayed at the `nslookup` prompt are for the closest center caches.
6	Examine the `x-grm-method` field in the GRM server access log to determine why the GRM DNS server returned each center cache. See Using the GRM server access log for test verification for information about accessing and using the GRM server access log. If the IP addresses returned by the GRM DNS server are not the IP addresses you expected, see Troubleshooting GRM configuration issues for troubleshooting information.
7	Return to the `nslookup` session, exit `nslookup`, and restart it. Exiting `nslookup` causes the client to revert to its local DNS nameserver.
8	Repeat Steps 4 and 5.
9	Check the GRM server access log to verify that the IP address of the local DNS nameserver matches the IP address listed for the DNS lookup in Step 4. If the IP address returned by the GRM DNS server does not match, see Troubleshooting GRM configuration issues for troubleshooting information.

Verifying GRM redirection for clients outside of edge groups for a GRM L7 server

For a GRM L7 server, to verify that clients not associated with edge groups are directed to the closest center caches, complete the following step.

Step

Action

Examine the x-grm-method field in the GRM server access log to determine why the GRM L7 server returned each center cache.

See Using the GRM server access log for test verification for information about accessing and using the GRM server access log.

If the IP addresses returned by the GRM L7 server are not the IP addresses you expected, see Troubleshooting GRM configuration issues for troubleshooting information.

Verifying edge cache failover for a GRM DNS server

For a GRM DNS server, to verify that center caches are returned when all edge caches in an edge group are unavailable, complete the following steps.

Step	Action
1	Log on to a workstation located within the edge group.
2	Halt all of the edge caches in the edge group.
3	Wait one minute to ensure that the GRM DNS server identifies that all edge caches have halted.
4	Enter the following command: nslookup After entering the preceding command, the `nslookup` prompt is displayed. For example: `>`
5	At the `nslookup` prompt, initiate a DNS lookup to a domain controlled by the GRM DNS server. For example: > images.cdn.company.com After the preceding command has been executed, the IP addresses of center caches returned by the GRM DNS server should be displayed. No edge cache IP addresses should be returned. If no center caches are returned or if edge caches are returned, see Troubleshooting the GRM configuration.

Verifying edge cache failover for a GRM L7 server

For a GRM L7 server, to verify that center caches are returned when all edge caches in an edge group are unavailable, complete the following step.

Step

Action

Examine the x-grm-method field in the GRM server access log to verify that center caches were returned.

See Using the GRM server access log for test verification for information about accessing and using the GRM server access log.