|
|
This chapter describes how to configure the IP address, subnet mask, and default gateway on the Catalyst 6000 family switches.
This chapter consists of these sections:
The Catalyst 6000 family switches have two configurable IP management interfaces, the in-band (sc0) interface and the Serial Line Internet Protocol (SLIP) (sl0) interface.
The in-band (sc0) management interface is connected to the switching fabric and therefore participates in all of the functions of a normal switch port, such as spanning tree, Cisco Discovery Protocol (CDP), VLAN membership, and so forth. The out-of-band management interface ( sl0) is not connected to the switching fabric and does not participate in any of these functions.
When you configure the IP address, subnet mask, broadcast address, and VLAN membership of the sc0 interface, you can access the switch through Telnet or Simple Network Management Protocol (SNMP). When you configure the SLIP (sl0) interface, you can open a point-to-point connection to the switch through the console port from a workstation.
All IP traffic generated by the switch itself (for example, a Telnet session opened from the switch to a host) is forwarded according to the entries in the switch IP routing table. For intersubnetwork communication to occur, you must configure at least one default gateway for the sc0 interface. The switch IP routing table is used to forward traffic originating on the switch only, not for forwarding traffic sent by devices connected to the switch.
These sections describe how the switch can obtain its IP configuration automatically:
The switch can obtain its IP configuration automatically using one of the following protocols:
The switch makes BOOTP, DHCP, and RARP requests only if the sc0 interface IP address is set to 0.0.0.0 when the switch boots up. This address is the default for a new switch or a switch whose configuration file has been cleared using the clear config all command. BOOTP, DHCP, and RARP requests are only broadcast out the sc0 interface.
There are three methods for obtaining an IP address from the DHCP server:
In addition to the sc0 interface IP address, the switch can obtain the subnet mask, broadcast address, and default gateway address. DHCP-learned values are not used if user-configured values are present.
The switch broadcasts a DHCPDISCOVER message one to ten seconds after all of the switch ports are online. The switch always requests an infinite lease time in the DHCPDISCOVER message.
If a DHCP or Bootstrap Protocol (BOOTP) server responds to the request, the switch takes appropriate action. If a DHCPOFFER message is received from a DCHP server, the switch processes all supported options contained in the message. Table 3-1 shows the supported DHCP options. Other options specified in the DHCPOFFER message are ignored.
| Code | Option |
|---|---|
1 | Subnet mask |
2 | Time offset |
3 | Router |
6 | Domain name server |
12 | Host name |
15 | Domain name |
28 | Broadcast address |
33 | Static route |
42 | NTP servers |
51 | IP address lease time |
52 | Option overload |
61 | Client-identifier |
66 | TFTP server name |
If a BOOTP response is received from a BOOTP server, the switch sets the in-band (sc0) interface IP address to the address specified in the BOOTP response.
If no DHCPOFFER message or BOOTP response is received in reply, the switch rebroadcasts the request using an exponential backoff algorithm (the amount of time between requests increases exponentially). If no response is received after ten minutes, the sc0 interface IP address remains set to 0.0.0.0 (provided that BOOTP and RARP requests fail as well).
If you reset or power cycle a switch with a DHCP- or BOOTP-obtained IP address, the information learned from DHCP or BOOTP is retained. At boot up, the switch attempts to renew the lease on the IP address. If no reply is received, the switch retains the current IP address.
With BOOTP and RARP, you map the switch MAC address to an IP address on the BOOTP or RARP server. The switch retrieves its IP address from the server automatically when it boots up.
The switch broadcasts 10 BOOTP and RARP requests after all of the switch ports are online. If a response is received, the switch sets the in-band (sc0) interface IP address to the address specified in the response.
If no reply is received, the sc0 interface IP address remains set to 0.0.0.0 (provided that DHCP requests fail as well).
If you reset or power cycle a switch with a BOOTP or RARP-obtained IP address, the information learned from BOOTP or RARP is retained.
Before you configure the switch IP address and default gateway, obtain the following information, as appropriate:
Table 3-2 shows the default IP address and default gateway configuration.
| Feature | Default Value |
|---|---|
In-band (sc0) interface |
|
Default gateway address | Set to 0.0.0.0 with a metric of 0 |
SLIP1 (sl0) interface |
|
| 1SLIP=Serial Line Internet Protocol |
Before you can Telnet to the switch or use SNMP to manage the switch, you must assign an IP address to the in-band (sc0) logical interface.
You can specify the subnet mask (netmask) using the number of subnet bits or using the subnet mask in dotted decimal format.
To set the IP address and VLAN membership of the in-band (sc0) management interface, perform this task in privileged mode:
| Task | Command |
|---|---|
set interface sc0 [ip_addr[/netmask] [broadcast]] | |
Step 2 Assign the in-band interface to the proper VLAN (make sure the VLAN is associated with the network to which the IP address belongs). | set interface sc0 [vlan] |
Step 3 If necessary, bring the interface up. | set interface sc0 up |
Step 4 Verify the interface configuration. | show interface |
This example shows how to assign an IP address, specify the number of subnet bits, and specify the VLAN assignment for the in-band (sc0) interface:
Console> (enable) set interface sc0 172.20.52.124/29 Interface sc0 IP address and netmask set. Console> (enable) set interface sc0 5 Interface sc0 vlan set. Console> (enable)
This example shows how to specify the VLAN assignment, assign an IP address, specify the subnet mask in dotted decimal format, and verify the configuration:
Console> (enable) set interface sc0 5 172.20.52.124/255.255.255.248
Interface sc0 vlan set, IP address and netmask set.
Console> (enable) show interface
sl0: flags=51<UP,POINTOPOINT,RUNNING>
slip 0.0.0.0 dest 0.0.0.0
sc0: flags=63<UP,BROADCAST,RUNNING>
vlan 5 inet 172.20.52.124 netmask 255.255.255.248 broadcast 172.20.52.17
Console> (enable)
The supervisor engine sends IP packets destined for other IP subnets to the default gateway (typically a router interface in the same network or subnet as the switch IP address). The switch does not use the IP routing table to forward traffic from connected devices, only IP traffic generated by the switch itself (for example, Telnet, TFTP, and ping).
You can define up to three default IP gateways. Use the primary keyword to make a gateway the primary gateway. If you do not specify a primary default gateway, the first gateway configured is the primary gateway. If more than one gateway is designated as primary, the last primary gateway configured is the primary default gateway.
The switch sends all off-network IP traffic to the primary default gateway. If connectivity to the primary gateway is lost, the switch attempts to use the backup gateways in the order they were configured. The switch sends periodic ping messages to determine whether each default gateway is up or down. If connectivity to the primary gateway is restored, the switch resumes sending traffic to the primary.
To specify one or more default gateways, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Configure a default IP gateway address for the switch. | set ip route default gateway [metric] [primary] |
Step 2 (Optional) Configure additional default gateways for the switch. | set ip route default gateway [metric] [primary] |
Step 3 Verify that the default gateways appear correctly in the IP routing table. | show ip route |
To remove default gateway entries, perform one of these tasks in privileged mode:
| Task | Command |
|---|---|
| clear ip route default gateway |
| clear ip route all |
This example shows how to configure three default gateways on the switch and how to verify the default gateway configuration:
Console> (enable)set ip route default 10.1.1.10Route added.Console> (enable)set ip route default 10.1.1.20Route added.Console> (enable)set ip route default 10.1.1.1 primaryRoute added.Console> (enable)show ip routeFragmentation Redirect Unreachable------------- -------- -----------enabled enabled enabledThe primary gateway: 10.1.1.1Destination Gateway RouteMask Flags Use Interface--------------- --------------- ---------- ----- -------- ---------default 10.1.1.1 0x0 UG 6 sc0default 10.1.1.20 0x0 G 0 sc0default 10.1.1.10 0x0 G 0 sc010.0.0.0 10.1.1.100 0xff000000 U 75 sc0default default 0xff000000 UH 0 sl0Console> (enable)
Use the SLIP (sl0) interface for point-to-point SLIP connections between the switch and an IP host.
To enable and attach SLIP on the console port, perform this task:
| Task | Command |
|---|---|
Step 1 Access the switch from a remote host with Telnet. | telnet {host_name | ip_addr} |
Step 2 Enter privileged mode on the switch. | enable |
Step 3 Set the console port SLIP address and the destination address of the attached host. | set interface sl0 slip_addr dest_addr |
Step 4 Verify the SLIP interface configuration. | show interface |
Step 5 Enable SLIP for the console port. | slip attach |
To disable SLIP on the console port, perform this task:
| Task | Command |
|---|---|
Step 1 Access the switch from a remote host with Telnet. | telnet {host_name | ip_addr} |
Step 2 Enter privileged mode on the switch. | enable |
Step 3 Disable SLIP for the console port. | slip detach |
This example shows how to configure SLIP on the console port and verify the configuration:
sparc20% telnet 172.20.52.38
Trying 172.20.52.38 ...
Connected to 172.20.52.38.
Escape character is '^]'.
Cisco Systems, Inc. Console
Enter password:
Console> enable
Enter password:
Console> (enable) set interface sl0 10.1.1.1 10.1.1.2
Interface sl0 slip and destination address set.
Console> (enable) show interface
sl0: flags=51<UP,POINTOPOINT,RUNNING>
slip 10.1.1.1 dest 10.1.1.2
sc0: flags=63<UP,BROADCAST,RUNNING>
vlan 522 inet 172.20.52.38 netmask 255.255.255.240 broadcast 172.20.52.7
Console> (enable) slip attach
Console Port now running SLIP.
Console> (enable) slip detach
SLIP detached on Console port.
Console> (enable)
To use BOOTP, DHCP, or RARP to obtain an IP address for the switch, perform this task:
| Task | Command |
|---|---|
Step 1 Make sure there is a DHCP, BOOTP, or RARP server on the network. |
|
Step 2 Obtain the last address in the MAC address range for module 1 (the supervisor engine). This address is displayed under the MAC-Address(es) heading. (With DHCP, this step is necessary only if using the manual allocation method.) | show module |
Step 3 Add an entry for each switch in the DHCP, BOOTP, or RARP server configuration, mapping the MAC address of the switch to the IP configuration information for the switch. (With DHCP, this step is necessary only if using the manual or automatic allocation methods.) |
|
Step 4 Set the sc0 interface IP address to 0.0.0.0. | set interface sc0 0.0.0.0 |
Step 5 Reset the switch. The switch broadcasts DHCP and RARP requests only when the switch boots up. | reset system |
Step 6 When the switch reboots, confirm that the sc0 interface IP address, subnet mask, and broadcast address are set correctly. | show interface |
Step 7 For DHCP, confirm that other options (such as default gateway address) are set correctly. | show ip route |
This example shows the switch broadcasting a DHCP request, receiving a DHCP offer, and configuring the IP address and other IP parameters according to the contents of the DHCP offer:
Console> (enable)
Sending RARP request with address 00:90:0c:5a:8f:ff
Sending DHCP packet with address: 00:90:0c:5a:8f:ff
dhcpoffer
Sending DHCP packet with address: 00:90:0c:5a:8f:ff
Timezone set to '', offset from UTC is 7 hours 58 minutes
Timezone set to '', offset from UTC is 7 hours 58 minutes
172.16.30.32 added to DNS server table as primary server.
172.16.31.32 added to DNS server table as backup server.
172.16.32.32 added to DNS server table as backup server.
NTP server 172.16.25.253 added
NTP server 172.16.25.252 added
%MGMT-5-DHCP_S:Assigned IP address 172.20.25.244 from DHCP Server 172.20.25.254
Console> (enable) show interface
sl0: flags=51<UP,POINTOPOINT,RUNNING>
slip 0.0.0.0 dest 0.0.0.0
sc0: flags=63<UP,BROADCAST,RUNNING>
vlan 1 inet 172.20.25.244 netmask 255.255.255.0 broadcast 172.20.25.255
dhcp server: 172.20.25.254
Console>
If you are using DHCP for IP address assignment, you can perform either of these DHCP-related tasks:
To renew or release a DHCP-assigned IP address on the in-band (sc0) management interface, perform one of these tasks in privileged mode:
| Task | Command |
|---|---|
| set interface sc0 dhcp renew |
| set interface sc0 dhcp release |
This example shows how to renew the lease on a DHCP-assigned IP address:
Console> (enable) set interface sc0 dhcp renew Renewing IP address... Console> (enable) Sending DHCP packet with address: 00:90:0c:5a:8f:ff <...output truncated...>
This example shows how to release the lease on a DHCP-assigned IP address:
Console> (enable) set interface sc0 dhcp release Releasing IP address... Console> (enable) Sending DHCP packet with address: 00:90:0c:5a:8f:ff Done Console> (enable)
Posted: Mon Feb 21 16:24:39 PST 2000
Copyright 1989 - 2000©Cisco Systems Inc.