Operating instructions

Chapter 8. Cisco Systems IGESM troubleshooting 221
Upstream Interfaces :
Downstream Interfaces :
(Up):Interface up (Dwn):Interface Down (Dis):Interface disabled
Make sure upstream interfaces include the expected interfaces. Upstream interfaces should
show all up if everything is working correctly.
Make sure downstream interfaces include the expected interfaces (may be all interfaces,
depending on desired config). Any configured downstream interfaces should show Up
.
Downstream ports will go to Dis when all configured upstream ports for the group go dow.n
show arp
Useful when troubleshooting connectivity issues between the IGESMs mgmt interface and
upstream connections or the Management Module, show arp is also handy for
troubleshooting connectivity issues to the management VLAN interface of the IGESM.
ARP table shows that a device (the IGESM in this case) could resolve the MAC address for a
given IP address.
ARP resolution is the first thing that happens when a device attempts to talk to another IP
address. (It knows the IP address, but it has to learn the MAC address to send directed
packets.)
cigesm_t#sh arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 172.26.146.1 105 0009.6bca.eba3 ARPA Vlan30
Internet 172.26.147.208 - 000f.90cd.6fc0 ARPA Vlan30
SPAN and RSPAN
SPAN and RSPAN are tools that can be used in conjunction with a network sniffer to capture
and analyze packets to and from a device. They can also be used to send data to an IDS
(Intrusion Detection System).
SPAN is used to switch monitored packets from a given port on this IGESM to a specific
physical port directly on this IGESM.
RSPAN is used to switch monitored packets to a special VLAN, and then carried to a remote
port not on this switch.
With both SPAN and RSPAN, you connected the sniffer to the port that is the destination of
the SPAN/RSPAN.
The use of SPAN and RSPAN are covered in 7.5.3, “Topology 3a: Dual Cisco Systems
IGESMs, two-port aggregation with RSPAN” on page 160the deployment Redpaper - in
Chapter 7.
Important: RSPAN should be used with caution, as it is possible to oversubscribe a link
with redirected traffic, which could result in dropped traffic.