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○ Either have a Linux server's ethernet port ip as the ERPM destination ip or connect the ingress interface of the
server to the ERPM MirrorToPort. The analyzer should listen in the forward/egress interface. If there is only one
interface, one can choose the ingress and forward interface to be same and listen in the tx direction of the interface.
○ Download/ Write a small script (for example: erpm.py) such that it will strip the given ERPM packet starting from
the bit where GRE header ends. Basically all the bits after 0x88BE need to be removed from the packet and sent out
through another interface.
○ This script erpm.zip is available for download at the following location: https://en.community.dell.com/techcenter/
networking/m/force10_networking_scripts/20438882.aspx
○ Unzip the erpm.zip and copy the erpm.py file to the Linux server.
○ Run the python script using the following command:
python erpm.py -i <ingress interface> -o <egress interface>
erpm.py : This is the script downloaded from the script store.
<Ingress interface> : Specify the interface id which is connected to the mirroring port or this should be interface whose ip
address has been specified as the destination ip address in the ERPM session.
<Egress interface> : Specify another interface on the Linux server via which the decapsulation packets can Egress. In case
there is only one interface, the ingress interface itself can be specified as Egress and the analyzer can listen in the tx direction.
Port Monitoring on VLT
Devices on which VLT is configured are seen as a single device in the network. You can apply port monitoring function on the
VLT devices in the network.
Port monitoring enables ingress or egress traffic traversing on a port to be sent to another port so that the traffic can be
analyzed. The port to which traffic is sent for analysis is called the mirroring port. This port is connect to a port analyzer, which
performs the traffic analysis function.
Depending up on the location of the port to which the port analyzer is connected, port monitoring is classified into three
categories: local Port mirroring, remote port mirroring (RPM), and encapsulated remote port mirroring (ERPM).
In VLT RPM, Dell EMC Networking OS supports only 3 Mirror-to-Port (MTPs) in hardware.
By default, 2 MTPs are used for ICL lag in VLT. The remaining one MTP is used to mirror only in one direction, either rx or tx.
NOTE: For more information on port monitoring, see Port Monitoring.
The port monitoring or mirroring function when applied to VLT devices works as expected except with some restrictions. You
can configure RPM or ERPM monitoring between two VLT peers. As VLT devices are seen as a single device in the network,
when a fail over occurs, the source or destination port on one of the VLT peers becomes inactive causing the monitoring session
to fail. As a result, Dell EMC Networking OS does not allow local Port mirroring based monitoring to be configured between VLT
peers. However, you can create local Port mirroring monitoring sessions separately on individual devices that are a part of the
VLT configuration.
NOTE: For more information on configuring VLT, see Configuring VLT on page 991.
VLT Non-fail over Scenario
Consider a scenario where port monitoring is configured to mirror traffic on a VLT device's port or LAG to a destination port on
some other device (TOR) on the network. When there is no fail over to the VLT peer, the VLTi link (ICL LAG) also receives the
mirrored traffic as the VLTi link is added as an implicit member of the RPM vlan. As a result, the mirrored traffic also reaches the
peer VLT device effecting VLTi link's bandwidth usage.
To mitigate this issue, the L2 VLT egress mask drops the duplicate packets that egress out of the VLT port. If the LAG status of
the peer VLT device is OPER-UP, then the other VLT peer blocks the transmission of packets received through VLTi to its port
or LAG. As a result, the destination port on the device to which the packet analyzer is connected does not receive duplicate
mirrored packets.
Port Monitoring
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