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Cisco IOS XR software Host Services and Applications features on the router are used primarily for checking network connectivity and the route a packet follows to reach a destination, mapping a hostname to an IP address or an IP address to a hostname, and transferring files between routers and UNIX workstations.
Network connectivity tools enable you to check device connectivity by running traceroutes and pinging devices on the network:
The ping command is a common method for troubleshooting the accessibility of devices. It uses two Internet Control Message Protocol (ICMP) query messages, ICMP echo requests, and ICMP echo replies to determine whether a remote host is active. The ping command also measures the amount of time it takes to receive the echo reply.
The ping command first sends an echo request packet to an address, and then it waits for a reply. The ping is successful only if the echo request gets to the destination, and the destination is able to get an echo reply (hostname is alive) back to the source of the ping within a predefined time interval.
The bulk option has been introduced to check reachability to multiple destinations. The destinations are directly input through the CLI. This option is supported for ipv4 destinations only.
As an aid to diagnosing basic network connectivity, many network protocols support an echo protocol. The protocol involves sending a special datagram to the destination host, then waiting for a reply datagram from that host. Results from this echo protocol can help in evaluating the path-to-host reliability, delays over the path, and whether the host can be reached or is functioning.
The following configuration shows an extended ping command sourced from the Router A TenGigEinterface and destined for the Router B TenGigE interface. If this ping succeeds, it is an indication that there is no routing problem. Router A knows how to get to the TenGigEinterface of Router B, and Router B knows how to get to the TenGigE interface of Router A. Also, both hosts have their default gateways set correctly.
If the extended ping command from Router A fails, it means that there is a routing problem. There could be a routing problem on any of the three routers: Router A could be missing a route to the subnet of Router B's interface, or to the subnet between Router C and Router B; Router B could be missing a route to the subnet of Router A's subnet, or to the subnet between Router C and Router A; and Router C could be missing a route to the subnet of Router A's or Router B's Ethernet segments. You should correct any routing problems, and then Host 1 should try to ping Host 2. If Host 1 still cannot ping Host 2, then both hosts' default gateways should be checked. The connectivity between the TenGigE interface of Router A and the TenGigE interface of Router B is checked with the extended ping command.
With a normal ping from Router A to Router B's TenGigE interface, the source address of the ping packet would be the address of the outgoing interface; that is the address of the TenGigE interface, (10.0.0.2). When Router B replies to the ping packet, it replies to the source address (that is, 10.0.0.2). This way, only the connectivity between the TenGigE interface of Router A (10.0.0.2) and the 10gige interface of Router B (10.0.0.1) is tested.
To test the connectivity between Router A's TenGigE interface (10.0.0.2) and Router B's TenGigE interface (10.0.0.1 .), we use the extended ping command. With extended ping, we get the option to specify the source address of the ping packet.
In this use case, the extended ping command verifies the IP connectivity between the two IP addresses Router A (10.0.0.2) and Router B (10.0.0.1) .
Router# ping 10.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5)
Router#!!!!!
*/If you do not enter a hostname or an IP address on the same line as the ping command,
the system prompts you to specify the target IP address and several other command parameters.
After specifying the target IP address, you can specify alternate values for the
remaining parameters or accept the displayed default for each parameter /*
Router# ping
Protocol [ipv4]:
Target IP address: 10.0.0.1
Repeat count [5]: 5
Datagram size [100]: 1000
Timeout in seconds [2]: 1
Interval in milliseconds [10]: 1
Extended commands? [no]: no
Sweep range of sizes? [no]:
Type escape sequence to abort.
Sending 5, 1000-byte ICMP Echos to 10.0.0.1, timeout is 1 seconds:
!!!!!
Success rate is 100 percent (5/5)
Router#!!!!!The bulk option enables you to check reachability to multiple destinations. The destinations are directly input through the CLI. This option is supported for ipv4 destinations only.
1: 1.1.1.1
2: 2.2.2.2
3: 3.3.3.3
Router# ping bulk ipv4 input cli batch
*/You must hit the Enter button and then specify one destination address per line*/
Please enter input via CLI with one destination per line and when done Ctrl-D/(exit) to initiate pings:
1: 1.1.1.1
2: 2.2.2.2
3: 3.3.3.3
4:
Starting pings...
Target IP address: 1.1.1.1
Repeat count [5]: 5
Datagram size [100]: 1
% A decimal number between 36 and 18024.
Datagram size [100]: 1
% A decimal number between 36 and 18024.
Datagram size [100]: 1000
Timeout in seconds [2]: 1
Interval in milliseconds [10]: 10
Extended commands? [no]: no
Sweep range of sizes? [no]: q
% Please answer 'yes' or 'no'.
Sweep range of sizes? [no]: q
% Please answer 'yes' or 'no'.
Sweep range of sizes? [no]:
Type escape sequence to abort.
Sending 5, 1000-byte ICMP Echos to 1.1.1.1, vrf is default, timeout is 1 seconds:
!!!!!
Success rate is 100 percent (5/5),
Target IP address: 2.2.2.2
Repeat count [5]:
Datagram size [100]: q
% A decimal number between 36 and 18024.
Datagram size [100]:
Timeout in seconds [2]:
Interval in milliseconds [10]:
Extended commands? [no]:
Sweep range of sizes? [no]:
Sending 5, 100-byte ICMP Echos to 1.1.1.1, vrf is default, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5),
Target IP address: 3.3.3.3
Repeat count [5]: 4
Datagram size [100]: 100
Timeout in seconds [2]: 1
Interval in milliseconds [10]: 10
Extended commands? [no]: no
Sweep range of sizes? [no]: no
Sending 4, 100-byte ICMP Echos to 1.1.1.1, vrf is default, timeout is 1 seconds:
!!!!!
Success rate is 100 percent (4/5),Where the ping command can be used to verify connectivity between devices, the traceroute command can be used to discover the paths packets take to a remote destination and where routing breaks down.
The traceroute command records the source of each ICMP "time-exceeded" message to provide a trace of the path that the packet took to reach the destination. You can use the IP traceroute command to identify the path that packets take through the network on a hop-by-hop basis. The command output displays all network layer (Layer 3) devices, such as routers, that the traffic passes through on the way to the destination.
The traceroute command uses the Time To Live (TTL) field in the IP header to cause routers and servers to generate specific return messages. The traceroute command sends a User Datagram Protocol (UDP) datagram to the destination host with the TTL field set to 1. If a router finds a TTL value of 1 or 0, it drops the datagram and sends back an ICMP time-exceeded message to the sender. The traceroute facility determines the address of the first hop by examining the source address field of the ICMP time-exceeded message.
To identify the next hop, the traceroute command sends a UDP packet with a TTL value of 2. The first router decrements the TTL field by 1 and sends the datagram to the next router. The second router sees a TTL value of 1, discards the datagram, and returns the time-exceeded message to the source. This process continues until the TTL increments to a value large enough for the datagram to reach the destination host (or until the maximum TTL is reached).
To determine when a datagram reaches its destination, the traceroute command sets the UDP destination port in the datagram to a very large value that the destination host is unlikely to be using. When a host receives a datagram with an unrecognized port number, it sends an ICMP port unreachable error to the source. This message indicates to the traceroute facility that it has reached the destination.
The traceroute command allows you to trace the routes that packets actually take when traveling to their destinations.
Trace the route from 10.0.0.2 to 20.1.1.1:
Router# traceroute 20.1.1.1
Type escape sequence to abort.
Tracing the route to 20.1.1.1
1 10.0.0.1 39 msec * 3 msec
*/If you do not enter a hostname or an IP address on the same line as the traceroute
command, the system prompts you to specify the target IP address and several other
command parameters. After specifying the target IP address, you can specify alternate
values for the remaining parameters or accept the displayed default for each
parameter/*
Router #traceroute
Protocol [ipv4]:
Target IP address: 20.1.1.1
Source address: 10.0.0.2
Numeric display? [no]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 20.1.1.1
1 10.0.0.1 3 msec * 3 msecCisco IOS XR software domain services acts as a Berkeley Standard Distribution (BSD) domain resolver. The domain services maintains a local cache of hostname-to-address mappings for use by applications, such as Telnet, and commands, such as ping and traceroute . The local cache speeds the conversion of host names to addresses. Two types of entries exist in the local cache: static and dynamic. Entries configured using the domain ipv4 host or domain ipv6 host command are added as static entries, while entries received from the name server are added as dynamic entries.
The name server is used by the World Wide Web (WWW) for translating names of network nodes into addresses. The name server maintains a distributed database that maps hostnames to IP addresses through the DNS protocol from a DNS server. One or more name servers can be specified using the domain name-server command.
When an application needs the IP address of a host or the hostname of an IP address, a remote-procedure call (RPC) is made to the domain services. The domain service looks up the IP address or hostname in the cache, and if the entry is not found, the domain service sends a DNS query to the name server.
You can specify a default domain name that Cisco IOS XR software uses to complete domain name requests. You can also specify either a single domain or a list of domain names. Any IP hostname that does not contain a domain name has the domain name you specify appended to it before being added to the host table. To specify a domain name or names, use either the domain name or domain list command.
DNS-based hostname-to-address translation is enabled by default. If hostname-to-address translation has been disabled using the domain lookup disable command, re-enable the translation using the no domain lookup disable command.
Define a static hostname-to-address mapping. Associate (or map) the IPv4 addresses (192.168.7.18 and 10.2.0.2 192.168.7.33) with two hosts. The host names are host1 and host2.
Defining the Domain Host
==================================
Router# configure
Router(config)#domain ipv4 host host1 192.168.7.18
Router(config)#domain ipv4 host host2 10.2.0.2 192.168.7.33
Router(config)#commit
Defining the Domain Name
==========================
*/Define cisco.com as the default domain name/*
Router#configure
Router(config)#domain name cisco.com
Router(config)#commit
Specifying the Addresses of the Name Servers
=============================================
*/Specify host 192.168.1.111 as the primary name server
and host 192.168.1.2 as the secondary server/*
Router#configure
Router(config)#domain name-server 192.168.1.111
Router(config)#domain name-server 192.168.1.2
Router(config)#commitRouter#show hosts
Default domain is cisco.com
Name/address lookup uses domain service
Name servers: 192.168.1.111, 192.168.1.2
Host Flags Age(hr) Type Address(es)
host2 (perm, OK) 0 IP 10.2.0.2
192.168.7.33
host1 (perm, OK) 0 IP 192.168.7.18It is expensive and inefficient to have a machine that acts only as a server on every network segment. However, when you do not have a server on every segment, your network operations can incur substantial time delays across network segments. You can configure a router to serve as a TFTP server to reduce costs and time delays in your network while you use your router for its regular functions.
Typically, a router that you configure as a TFTP server enables the router to serve requests from client routers. This includes services such as providing client routers with system image or router configuration files from its flash memory. You can also configure the router to respond to other types of service requests.
The server and client router must be able to reach each other before the TFTP function can be implemented. Verify this connection by testing the connection between the server and client router (in either direction) using the ping command.
This task allows you to configure the router as a TFTP server so other devices acting as TFTP clients are able to read and write files from and to the router under a specific directory, such as slot0:, /tmp, and so on (TFTP home directory).
 Note |
For security reasons, the TFTP server requires that a file must already exist for a write request to succeed. The server and client router must be able to reach each other before the TFTP function can be implemented. Verify this connection by testing the connection between the server and client router (in either direction) using the ping command. |
Configure the router (home directory disk0:) as the TFTP server.
Router#configure
Router(config)#tftp ipv4 server homedir disk0
Router(config)#commitRouter#show running-config tftp ipv4 server homedir disk0:
tftp vrf default ipv4 server homedir disk0:Router#show cinetd services
Vrf Name Family Service Proto Port ACL max_cnt curr_cnt wait Program Client Option
default v4 tftp udp 69 unlimited 0 wait tftpd sysdb disk0:
default v4 telnet tcp 23 10 0 nowait telnetd sysdb
File Transfer Protocol (FTP), Trivial File Transfer Protocol (TFTP), remote copy protocol (rcp) rcp clients, and Secure Copy Protocol (SCP) are implemented as file systems or resource managers. For example, path names beginning with tftp:// are handled by the TFTP resource manager.
The file system interface uses URLs to specify the location of a file. URLs commonly specify files or locations on the WWW. However, on Cisco routers, URLs also specify the location of files on the router or remote file servers.
When a router crashes, it can be useful to obtain a copy of the entire memory contents of the router (called a core dump) for your technical support representative to use to identify the cause of the crash. SCP, FTP, TFTP, rcp can be used to save the core dump to a remote server.
File Transfer Protocol (FTP) is part of the TCP/IP protocol stack, which is used for transferring files between network nodes. FTP is defined in RFC 959.
You can configure the router to use FTP connections for transferring files between systems on the network. You can set the following FTP characteristics:
Passive-mode FTP
Password
IP address
Enable the router to use FTP connections. Configure the software to use passive FTP connections, a password for anonymous users, and also specify the source IP address for FTP connections.
Router# configure
Router(config)# ftp client passive
Router(config)# ftp client anonymous-password xxxx
Router(config)# ftp client source-interface TenGigE 0/0/0/0
Router(config)# commitTrivial File Transfer Protocol (TFTP) is a simplified version of FTP that allows files to be transferred from one computer to another over a network, usually without the use of client authentication (for example, username and password).
Configure the router to use TFTP connections and set the IP address of the TenGigE interface 0/0/0/0 as the source address for TFTP connections:
Router# configure
Router (config)# tftp client source-interface TengGigE 0/0/0/0
Router (config)# commitRouter# show cinetd services
Vrf Name Family Service Proto Port ACL max_cnt curr_cnt wait Program Client Option
default v4 tftp udp 69 unlimited 0 wait tftpd sysdb disk0:
default v4 telnet tcp 23 10 0 nowait telnetd sysdb
Secure Copy Protocol (SCP) is a file transfer protocol which provides a secure and authenticated method for transferring files. SCP relies on SSHv2 to transfer files from a remote location to a local location or from local location to a remote location.
Cisco IOS XR software supports SCP server and client operations. If a device receives an SCP request, the SSH server process spawns the SCP server process which interacts with the client. For each incoming SCP subsystem request, a new SCP server instance is spawned. If a device sends a file transfer request to a destination device, it acts as the client.
When a device starts an SSH connection to a remote host for file transfer, the remote device can either respond to the request in Source Mode or Sink Mode. In Source Mode, the device is the file source. It reads the file from its local directory and transfers the file to the intended destination. In Sink Mode, the device is the destination for the file to be transferred.
Using SCP, you can copy a file from the local device to a destination device or from a destination device to the local device.
Using SCP, you can only transfer individual files. You cannot transfer a file from a destination device to another destination device.
Secure Copy Protocol (SCP) allows you to transfer files between source and destination devices. You can transfer one file at a time. If the destination is a server, SSH server process must be running.
Transfers the file "file1.txt" from the local directory to the remote directory and the "file2.txt" from vice-versa.
Router#scp /usr/file1.txt root@209.165.200.1:/root/file1.txt
** Transfers a file from a local directory to a remote directory**
Router# commit
Router#scp root@209.165.200.1:/root/file2.txt /usr/file2.txt
** Transfers a file from a remote directory to a local directory**
Router# commitCisco Internet services process daemon (Cinetd) is a multithreaded server process that is started by the system manager after the system has booted. Cinetd listens for Internet services such as Telnet service, TFTP service, and so on. Whether Cinetd listens for a specific service depends on the router configuration. For example, when the tftp server command is entered, Cinetd starts listening for the TFTP service. When a request arrives, Cinetd runs the server program associated with the service.
Enabling Telnet allows inbound Telnet connections into a networking device.
Enable telnet and limit the number of simultaneous users that can access the router to 10.
Router# configure
Router(config)# telnet ipv4 server max-servers 10
Router(config)# commitRouter# show cinetd services
Vrf Name Family Service Proto Port ACL max_cnt curr_cnt wait Program Client Option
default v4 tftp udp 69 unlimited 0 wait tftpd sysdb disk0:
default v4 telnet tcp 23 10 0 nowait telnetd sysdb
You can configure the logging source interface to identify the syslog traffic, originating in a VRF from a particular router, as coming from a single device.
Enable a source interface for the remote syslog server. Configure interface loopback 1 to be the logging source interface for the default vrf.
Router#configure
Router(config)#logging source-interface loopback 1 vrf default
Router(config)#commitRouter#show running-config logging
logging source-interface Loopback1
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