Identifying Core Link Issues
Question
A service provider NOC engineer received numerous support tickets from their VPN customers.
These customers are reporting packet loss between two PE routers.
The NOC engineer created a VRF TEMP to run tests between these two PE routers, and no errors were reported.
ECMP links are used between P and PE routers.
Which test can quickly identify the core link that is causing the problems?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D. E. F.B.
In this scenario, customers are reporting packet loss between two PE routers in a service provider network. The NOC engineer has created a VRF TEMP to run tests between these two PE routers and no errors were reported. The network uses ECMP links between P and PE routers. Now the NOC engineer needs to identify the core link that is causing the problems.
Option A: An extended traceroute with multipath option between the PE's loopbacks can help identify the path taken by packets between the PE routers. This test sends multiple probes at the same time along multiple paths and provides information on the latency and the packet loss experienced by each path. However, this option alone may not be able to identify the specific core link that is causing the problem.
Option B: An MPLS traceroute with multipath option between the PE's loopbacks can provide a similar result as option A, but with the addition of information on the MPLS labels and the forwarding path through the network. This can help identify the specific core link that is causing the problem, making it a better option than option A.
Option C: An MPLS ping with sweep option between the PE's loopbacks can send a series of MPLS echo requests with increasing TTL values to detect the path taken by the packets and to identify the specific core link that is causing the problem. This test can quickly identify the problematic link, making it a good option.
Option D: A VRF ping between the customer's CE router and the service provider's remote PE router can help identify any problems with the VRF configuration or the connectivity between the CE and PE routers. However, this test alone may not be able to identify the specific core link that is causing the problem.
Option E: An extended ping with sweep option between the PE's loopbacks can help identify the latency and packet loss between the two PE routers, but may not be able to identify the specific core link that is causing the problem.
Option F: A VRF traceroute between the customer's CE router and the service provider's remote PE router can help identify the path taken by the packets between the CE and PE routers and can help identify any routing problems in the VRF. However, this test alone may not be able to identify the specific core link that is causing the problem.
Therefore, options B and C are the most effective tests to quickly identify the specific core link that is causing the problem in this scenario.
