Configuring Transports

Information About Configuring NSR, TCP, UDP Transports

To configure NSR, TCP, UDP, and RAW transports, you must understand the following concepts:

NSR Overview

Table 1. Feature History Table

Feature Name

Release

Description

Nonstop Routing (NSR)

Release 24.4.1

Introduced in this release on: Fixed Systems (8700 [ASIC:K100])(select variants only*).

NSR ensures uninterrupted routing by maintaining protocol sessions during process restarts, thus enhancing network reliability. It eliminates session loss and minimizes packet drop by preserving the router's state and synchronizing it with standby processes. This reliability is particularly beneficial for maintaining stable connections in dynamic environments. By automatically synchronizing routing information, NSR provides seamless network operation and reduces the need for manual intervention during failures. This feature is essential for environments demanding continuous network availability and high resilience to faults.

*Previously this feature was supported on Q200 and Q100. It is now extended to Cisco 8712-MOD-M routers.

Nonstop Routing (NSR) is provided for Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), and Label Distribution Protocol (LDP) protocols for the following events:

  • Route Processor (RP) failover

  • Process restart for either OSPF, LDP, or TCP

  • Online insertion removal (OIR)

In the case of the RP failover, NSR is achieved by for both TCP and the applications (OSPF, BGP, or LDP).

NSR is a method to achieve High Availability (HA) of the routing protocols. TCP connections and the routing protocol sessions are migrated from the active RP to standby RP after the RP failover without letting the peers know about the failover. Currently, the sessions terminate and the protocols running on the standby RP reestablish the sessions after the standby RP goes active. Graceful Restart (GR) extensions are used in place of NSR to prevent traffic loss during an RP failover but GR has several drawbacks.

You can use the nsr process-failures switchover command to let the RP failover be used as a recovery action when the active TCP or active LDP restarts. When standby TCP or LDP restarts, only the NSR capability is lost till the standby instances come up and the sessions are resynchronized but the sessions do not go down. In the case of the process failure of an active OSPF, a fault-management policy is used.

For more information, refer to chapter Implementing OSPF Routing Configuration Guide for Cisco 8000 Series Routers.

TCP Overview

TCP is a connection-oriented protocol that specifies the format of data and acknowledgments that two computer systems exchange to transfer data. TCP also specifies the procedures the computers use to ensure that the data arrives correctly. TCP allows multiple applications on a system to communicate concurrently, because it handles all demultiplexing of the incoming traffic among the application programs.

UDP Overview

The User Datagram Protocol (UDP) is a connectionless transport-layer protocol that belongs to the IP family. UDP is the transport protocol for several well-known application-layer protocols, including Network File System (NFS), Simple Network Management Protocol (SNMP), Domain Name System (DNS), and TFTP.

Any IP protocol other than TCP and UDP is known as a RAW protocol.

For most sites, the default settings for the TCP, UDP, and RAW transports need not be changed.

Prerequisites for Configuring NSR, TCP, UDP, Transports

The following prerequisites are required to implement NSR, TCP, UDP, Transports:

You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Configuring Failover as a Recovery Action for NSR

When the active TCP or the NSR client of the active TCP terminates or restarts, the TCP sessions go down. To continue to provide NSR, failover is configured as a recovery action. If failover is configured, a switchover is initiated if the active TCP or an active application (for example, LDP, OSPF, and so forth) restarts or terminates.

For information on how to configure MPLS Label Distribution Protocol (LDP) for NSR, refer to the MPLS Configuration Guide for Cisco 8000 Series Routers.

For information on how to configure NSR on a per-process level for each process, refer to the Routing Configuration Guide for Cisco 8000 Series Routers.

Configuration Example

Configure failover as a recovery action for active instances to switch over to a standby to maintain nonstop routing. 

Router#configure
Router(config)#nsr process-failures switchover
Router(config)#commit

Running Configuration

Router#show running-configuration nsr process-failures switchover
nsr process-failures switchover

Associated Commands

  • nsr process-failures switchover

TCP Dump File Converter

Table 2. Feature History Table

Feature Name

Release Information

Feature Description

TCP Dump File Converter

Release 24.2.11

You can now convert an entire TCP dump of packet traces in binary files into readable formats such as text or cap, which makes it easier to analyze them for troubleshooting using third-party or open-source tools. This feature saves time and effort by preventing the need to examine each packet for failure.

This feature introduces the tcp dump-file convert command.

TCP dump file converter is a tool that converts tcp ios-xr dump-files in binary format to user-friendly format such as pcap or text.

It proves especially useful when you disable Non-Stop Routing (NSR) or experience a session flap on your router. During such incidents, by default, the tcp process running on the router promptly stores the latest 200 packet traces in binary format within a temporary folder.

TCPdump packet traces also includes data about the configured routing protocols and the overall network traffic traversing your system. This data equips you with the necessary insights to identify and resolve issues within your network infrastructure, facilitating proactive network troubleshooting.

You can view the packet traces binary files in the user-readable format using the following methods:

  • You can use the show tcp dump-file <binary filename> command to view each binary file in text format manually. For more information, refer to View Binary Files in Text Format Manually.

    This process consumes much time, as you have to view each file manually one after another.

  • From Release 24.2.11, you can convert all stored packet traces in binary files into a user-readable format such as pcap, text, or both using the tcp dump-file convert command. For more information, refer to Convert Binary Files to Readable Format Using TCP Dump File Converter.

    This active approach greatly improves the efficiency and ease of packet analysis during network troubleshooting.

Limitations and Restrictions for TCP Dump File Converter

  • Routers only store the most recent 200 message exchanges that occurred right before the session termination, when NSR is disabled, or during a session flap.

  • You can view only one binary file in text format using the show tcp dump-file <binary filename> command.

  • When the NSR is disabled, the tcp dump files are stored only for major protocols like border gateway protocol (BGP), multicast source discovery protocol (MSDP), and multiprotocol label switching label distribution protocol (MPLS LDP).

View Binary Files in Text Format Manually

Perform the following steps to view each packet traces binary file in text format without using the TCP dump file converter:

Procedure

Step 1

View the list of packet traces in binary files stored in the tcpdump folder using the show tcp dump-file list all command.

Example:

Router# show tcp dump-file list all
total 1176
-rw-r--r-- 1 root root 5927 Nov 22 12:42 31_0_0_126.179.20966.cl.1700656933
-rw-r--r-- 1 root root 5892 Nov 22 12:42 31_0_0_127.179.35234.cl.1700656933
-rw-r--r-- 1 root root 6148 Nov 22 12:42 31_0_0_149.179.54939.cl.1700656933
-rw-r--r-- 1 root root 5894 Nov 22 12:42 31_0_0_155.179.18134.cl.1700656933
-rw-r--r-- 1 root root 6063 Nov 22 12:42 31_0_0_156.179.25445.cl.1700656933
-rw-r--r-- 1 root root 5860 Nov 22 12:42 31_0_0_161.179.30859.cl.1700656933
-rw-r--r-- 1 root root 5832 Nov 22 12:42 31_0_0_173.179.36935.cl.1700656933
-rw-r--r-- 1 root root 5906 Nov 22 12:42 31_0_0_190.179.25642.cl.1700656933

Step 2

View each packet traces binary file in text format using the show tcp dump-file <binary filename> command.

Example:

Router# show tcp dump-file 10_106_0_73.179.34849.cl.1707424077 location 0/RP0/CPU0 
Filename: 10_106_0_73.179.34849.cl.1707424077

==============================================================
Connection state is CLOSED, I/O status: 0, socket status: 103
PCB 0x00007f86bc05e3b8, SO 0x7f86bc05e648, TCPCB 0x7f86bc0c3718, vrfid 0x60000000, 
Pak Prio: Medium, TOS: 192, TTL: 1, Hash index: 1593
Local host: 10.106.0.72, Local port: 179 (Local App PID: 11354)
Foreign host: 10.106.0.73, Foreign port: 34849
(Local App PID/instance/SPL_APP_ID: 11354/1/0)

Current send queue size in bytes: 0 (max 0)
Current receive queue size in bytes: 0 (max 0)  mis-ordered: 0 bytes
Current receive queue size in packets: 0 (max 0)

Timer          Starts    Wakeups         Next(msec)
Retrans        103448          8                0
SendWnd             0          0                0
TimeWait            1          0                0
AckHold        106815     106545                0
KeepAlive           1          0                0
PmtuAger            0          0                0
GiveUp              0          0                0
Throttle            0          0                0
FirstSyn            0          0                0

   iss: 161240548   snduna: 163206936   sndnxt: 163206936 
sndmax: 163206936   sndwnd: 63104       sndcwnd: 18120     
   irs: 3691232436  rcvnxt: 3693473072  rcvwnd: 26099   rcvadv: 3693499171

The above sample displays only a part of the actual output; the actual output displays more details.

Convert Binary Files to Readable Format Using TCP Dump File Converter

Perform the following steps to convert the tcp dump packet traces in binary files into pcap and text formats:

Procedure

Step 1

Execute the tcp dump-file convert all-formats all command to convert the tcp dump packet traces in binary files into pcap and text formats.

Example:

Router# tcp dump-file convert all-formats all
ascii file is saved at : /harddisk:/decoded_dumpfiles/text_tcpdump_peer_all_node0_RP0_CPU0_2024_3_19_10_8_53.462070.txt
pcap file is saved at : /harddisk:/decoded_dumpfiles/pcap_tcpdump_peer_all_node0_RP0_CPU0_2024_3_19_10_8_40.154838.pcap
[OK]

By default, the router stored the converted files in the "decoded_dumpfiles" folder on the "hard disk".

Using the location node-id and file <file path> keywords, you can save the converted TCP dump file to your desired location.

For example, tcp dump-file convert all-formats all location 0/RP0/CPU0 file /harddisk:/demo2 .

For more information, refer to System Management Command Reference for Cisco NCS 5500 Series Routers tcp dump-file convert command. 

Router# tcp dump-file convert all-formats all location 0/RP0/CPU0 file /harddisk:/demo2
ascii file is saved at : /harddisk:/demo2.txt
pcap file is saved at : /harddisk:/demo2.pcap
[OK]

Step 2

To view the converted text file in the CLI, use the run cat <text file path> command.

Example:

Router# run cat /harddisk:/decoded_dumpfiles/text_tcpdump_peer_all_node0_RP0_CPU0_2024_3_19_10_8_53.462070.txt
Filename: 2024_3_19_10_8_53.462070

==============================================================
Connection state is CLOSED, I/O status: 0, socket status: 103
PCB 0x0000000000f47a80, SO 0xf476d0, TCPCB 0xf6a370, vrfid 0x60000000, 
Pak Prio: Medium, TOS: 192, TTL: 255, Hash index: 563
Local host: 14:11:11::1, Local port: 47743 (Local App PID: 19579)
Foreign host: 14:11:11::2, Foreign port: 179
(Local App PID/instance/SPL_APP_ID: 19579/1/0)

Current send queue size in bytes: 0 (max 0)
Current receive queue size in bytes: 0 (max 0)  mis-ordered: 0 bytes
Current receive queue size in packets: 0 (max 0)

Timer          Starts    Wakeups         Next(msec)
Retrans            70          2                0
SendWnd             0          0                0
TimeWait            2          0                0
AckHold            66         61                0
KeepAlive           1          0                0
PmtuAger            0          0                0
GiveUp              0          0                0
Throttle            0          0                0
FirstSyn            1          1                0

   iss: 3113104891  snduna: 3113106213  sndnxt: 3113106213
sndmax: 3113106213  sndwnd: 31523       sndcwnd: 2832      
   irs: 4250126727  rcvnxt: 4250128049  rcvwnd: 31448   rcvadv: 4250159497

The above sample displays only a part of the actual output; the actual output displays more details.

Step 3

Use remote file copy commands like scp from your lab server to copy the converted packet traces from the router to your local computer and view the converted pcap file.