Cisco Virtual Security Gateway for Nexus 1000V Series Switch Troubleshooting Guide, Release 4.2(1)VSG1(3.1)
Chapter 8 - Troubleshooting System Issues
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Troubleshooting System Issues

Table Of Contents

Troubleshooting System Issues

Information About the System

Problems with VM Traffic

VEM Troubleshooting Commands

Displaying VEM Information

Displaying Miscellaneous VEM Details

VEM Log Commands

Troubleshooting the Cisco VSG in the Layer 3 Mode

show vsn brief Command Output Indicates Service Node State is Down

Cisco VSG with a VN Service vmknic in Layer 3 Mode

Cisco VSGs with Multiple l3-vn-service vmknics in Layer 3 Mode

Traffic with Large Payloads Fails: ICMP Too Big Message Does not Reach the Client with the Cisco VSG in Layer 3 Mode

End-to-End Traffic with the Cisco VSG in Layer 3 Mode Fails

End-to-End Traffic with the Cisco VSG in Layer 3 Mode and Jumbo Frames Fails

TCP State Checks

Connection Limit in VSG


Troubleshooting System Issues


This chapter describes how to troubleshoot Cisco Virtual Security Gateway (VSG) system issues.

This chapter includes the following sections:

Information About the System

Problems with VM Traffic

VEM Troubleshooting Commands

VEM Log Commands

Troubleshooting the Cisco VSG in the Layer 3 Mode

Information About the System

The Cisco VSG provides firewall functionality for the VMs that have the vEths with port profiles created by the Virtual Supervisor Module (VSM). To allow the Cisco VSG to function properly, the Cisco VSG should have registered with a Cisco Virtual Network Management Center (VNMC) and the Cisco VSG data interface MAC address should be seen by the VSM.

The example shows how to display information about the system:

vsg# show vsg
Model: VSG
HA ID: 218
VSG Software Version: 4.2(1)VSG1(1) build [4.2(1)VSG1(1)]
VNMC IP: 10.193.77.223
VSG-PERF-1_1#
VSG-PERF-1_1# show vnm-pa status
VNM Policy-Agent status is - Installed Successfully. Version 1.0(1j)-vsg
vsg# 

Make sure that the Cisco VSG MAC address is learned by the VSM by entering the show vsn details command as follows:

vsm# show vsn detail
#VSN  VLAN: 754, IP-ADDR: 200.1.1.10
  MODULE       VSN-MAC-ADDR  FAIL-MODE   VSN-STATE
       3  00:50:56:83:00:01      Close          Up
 
   
#VSN Ports, Port-Profile, Org and Security-Profile Association:
#VSN  VLAN: 754, IP-ADDR: 200.1.1.10
  Port-Profile: profile-traffic, Security-Profile: sec-profile-perf, Org: 
root/Tenant-perf-1.1
    Module  Vethernet
         3  9
vsm# 

For more information, see the following documents:

Cisco Virtual Security Gateway, Release 4.2(1)VSG1(1)

Cisco Virtual Network Management Center, Release 1.0.1 Installation

Quick Start Guide for Cisco Virtual Security Gateway and Cisco Virtual Network Management Center.

Problems with VM Traffic

When troubleshooting problems with intra-host VM traffic, follow these guidelines:

Make sure that at least one of the VMware virtual NICs is on the correct DVS port group and is connected.

If the VMware virtual NIC is down, determine if there is a conflict between the MAC address configured in the OS and the MAC addresses as that are assigned by VMware. You can see the assigned MAC addresses in the .vmx file.

When troubleshooting problems with inter-host VM traffic, follow these guidelines:

Determine if there is one uplink sharing a VLAN with the VMware virtual NIC. If there is more than one uplink, they must be in a port channel.

Ping an SVI on the upstream switch by entering the show intX counters command.

VEM Troubleshooting Commands

This section includes the following topics:

Displaying VEM Information

Displaying Miscellaneous VEM Details

Displaying VEM Information

Use the following commands to display Virtual Ethernet Module (VEM) information:

vemlogDisplays and controls VEM kernel logs

vemcmdDisplays configuration and status information

vem-support allDisplays support information

vem statusDisplays status information

vem versionDisplays version information

vemcmd show arp allDisplays the ARP table on the VEM

vemcmd show vsn configDisplays all the Cisco VSGs configured on the VEM and the Cisco VSG licensing status (firewall on or off)

vemcmd show vsn bindingDisplays all of the VM LTL ports to the Cisco VSG bindings

vemcmd show learntDisplays all of the VMs that have been learned by the VEM

Displaying Miscellaneous VEM Details

These commands provide additional VEM details:

vemlog show last number-of-entriesDisplays the circular buffer

This example shows how to display the number of entries in the circular buffer:

[root@esx-cos1 ~]# vemlog show last 5
Timestamp                  Entry CPU  Mod Lv         Message
Oct 13 13:15:52.615416      1095   1    1  4 Warning vssnet_port_pg_data_ ...
Oct 13 13:15:52.620028      1096   1    1  4 Warning vssnet_port_pg_data_ ...
Oct 13 13:15:52.630377      1097   1    1  4 Warning svs_switch_state ...
Oct 13 13:15:52.633201      1098   1    1  8    Info vssnet new switch ...
Oct 13 13:16:24.990236      1099   1    0  0         Suspending log
 
   

vemlog show info—Displays information about entries in the log

This example shows how to display log entries:

[root@esx-cos1 ~]# vemlog show info
          Enabled: Yes
    Total Entries: 1092
  Wrapped Entries: 0
     Lost Entries: 0
  Skipped Entries: 0
Available Entries: 6898
 Stop After Entry: Not Specified
 
   

vemcmd help—Displays the type of information you can display

This example shows how to display the vemcmd help:

[root@esx-cos1 ~]# vemcmd help
show card              Show the card's global info
show vlan [vlan]       Show the VLAN/BD table
show bd [bd]           Show the VLAN/BD table
show l2 <bd-number>    Show the L2 table for a given BD/VLAN
show l2 all            Show the L2 table
show port [priv|vsm]   Show the port table
show pc                Show the port channel table
show portmac           Show the port table MAC entries
show trunk [priv|vsm]  Show the trunk ports in the port table
show stats             Show port stats
 
   

VEM Log Commands

Use the following commands to control the vemlog:

vemlog stop—Stops the log

vemlog clearClears the log

vemlog start number-of-entriesStarts the log and stops it after the specified number of entries

vemlog stop number-of-entriesStops the log after the next specified number of entries

vemlog resumeStarts the log but does not clear the stop value

You can display the list of debug filters by entering the vemlog show debug | grp vpath command.

This example shows how to display the list of debug filters:

~ # vemlog show debug | grep vpath
               vpath       ENWID P ( 95)       ENW     (  7)
            vpathapi       ENWID P ( 95)       ENW     (  7)
             vpathfm       ENWID P ( 95)       ENW     (  7)
            vpathfsm       ENWID P ( 95)       ENW     (  7)
          vpathutils       ENWID P ( 95)       ENW     (  7)
            vpathtun       ENWID P ( 95)       ENW     (  7)
~ #

Troubleshooting the Cisco VSG in the Layer 3 Mode

This section includes the following topics:

show vsn brief Command Output Indicates Service Node State is Down

Traffic with Large Payloads Fails: ICMP Too Big Message Does not Reach the Client with the Cisco VSG in Layer 3 Mode

End-to-End Traffic with the Cisco VSG in Layer 3 Mode Fails

End-to-End Traffic with the Cisco VSG in Layer 3 Mode and Jumbo Frames Fails

TCP State Checks

Connection Limit in VSG

show vsn brief Command Output Indicates Service Node State is Down

This section includes the following topics:

Cisco VSG with a VN Service vmknic in Layer 3 Mode

Cisco VSGs with Multiple l3-vn-service vmknics in Layer 3 Mode

Cisco VSG with a VN Service vmknic in Layer 3 Mode

When encapsulated traffic that is destined to a Cisco VSG is connected to a different subnet other than the vmknic subnet, the VEM does not use the VMware host routing table. Instead, the vmknic initiates an Address Resolution Protocol (ARP) for the remote Cisco VSG IP addresses.

You must configure the upstream router to respond by using the proxy ARP feature. If the proxy ARP feature is not configured on the upstream router, the ARP fails and the show vsn brief indicates that the service node state is down.

To resolve this issue configure the proxy ARP feature on the router as follows:

sg-cat3k-L14-qa(config)# int vlan 3756
sg-cat3k-L14-qa(config-if)# ip proxy-arp
sg-cat3k-L14-qa(config-if)# end
sg-cat3k-L14-qa# sh ip int vlan 3756 | inc Proxy
  Proxy ARP is enabled
  Local Proxy ARP is disabled
sg-cat3k-L14-qa#

Cisco VSGs with Multiple l3-vn-service vmknics in Layer 3 Mode

The data path traffic and the ARP packets for the Cisco VSGs in Layer 3 mode can use any vmknic that is configured on the VEM host for packet forwarding to the Cisco VSG when you enter the capability l3-vn-service command.

Therefore, all vmknics that are on a VEM host must be able to reach all Cisco VSGs in Layer 3 mode.

If a router is between the vmknics and the Cisco VSGs, all vmknics must have an interface in the router network (VLAN), and all the Cisco VSGs in the Layer 3 mode must have an interface in the router network (VLAN) to ensure that each vmknic has a route to each Cisco VSG.

To resolve this issue ensure that all l3-vn-service vmknics can reach all the Cisco VSGs in the Layer 3 mode that are used by the VEM host.


Note You must enable Proxy ARP on all vmknics that facie interfaces on the router.


Traffic with Large Payloads Fails: ICMP Too Big Message Does not Reach the Client with the Cisco VSG in Layer 3 Mode

If a router lies between the vmknic and the Cisco VSG in the Layer 3 mode, and the router receives a packet that it cannot forward due to a large packet size, the router generates an ICMP Too Big message for the vmknic. The vmknic cannot forward the ICMP Too Big message of the router to the client and the vmknic drops the message. The client never receives the ICMP Too Big message and cannot refragment the packet for successful end-to-end traffic and the end-to-end traffic fails. This problem is typically seen if the router interface to the VEM is set at a higher maximun transmission unit (MTU) than the router interface to the Cisco VSG. For example, the router interface to the VEM has an MTU of 1600 and the interface to the Cisco VSG has an MTU of 1500.

This problem can be seen as an increase in the ICMP Too Big Rcvd counter in the show vsn statistics command.

To resolve this issue, configure an oversized MTU (for example, 1600) on both of the router interfaces.

End-to-End Traffic with the Cisco VSG in Layer 3 Mode Fails

When the VEM communicates with the Cisco VSG in the Layer 3 mode, an additional header with 94 bytes is added to the original packet. The VEM does not support fragmentation in the Layer 3 mode and the ports or network elements (which carry a vPath encapsulated packet) must be configured in such a way that the vPath overhead is accommodated.

If end-to-end traffic fails with a Cisco VSG Layer 3 mode, set the uplink MTU to 1594 bytes to accommodate the additional overhead. This solution assumes that the client and server VM MTUs are at the default of 1500 bytes.

End-to-End Traffic with the Cisco VSG in Layer 3 Mode and Jumbo Frames Fails

Traffic with the Layer 3 encapsulation fails even with the uplink MTU set to 9000 bytes.

If jumbo frames are enabled in the network and the end-to-end traffic fails, make sure that the MTU of the client and server VMs are 94 bytes smaller than the uplink. For example, if the uplink MTU is 9000, set the MTU of the client and server VMs to 8906 bytes.

TCP State Checks

By default, TCP state checks are enabled in vPath for the traffic protected by the Cisco VSG. Sometimes, you might see delays in the TCP traffic. You can disable TCP state checks to diagnose the issue.

Check the following counters at the VSM in show vsn statistics output:

VSM # show vsn statistics vpath | grep "TCP chkfail"

TCP chkfail InvalACK 0        TCP chkfail SeqPstWnd   0

TCP chkfail WndVari 0

This example shows how to disable the TCP state checks on a VSM:

VSM(config)# vsn type vsg global 
VSM(config-vsn)# no tcp state-checks 
VSM(config-vsn)# 

Connection Limit in VSG

The Cisco VSG can have up to 256,000 active connections at any given point of time. If for some reason new connections slows down or connections see too many failures, you can check the Cisco VSG for any connection limits that it experiences. If the VEM-to-Cisco VSG connection is not smooth or have some issues that indicates that the Cisco VSG might have missed a few updates from vPath which results in an accumulation of large active connections in its flow table.

This example shows how to check the active connection count on the Cisco VSG:

VSG# show service-path statistics | inc "Active Connections"

Active Flows 48 Active Connections 24

VSG#