Configuring Basic IPv4 IS-IS Functions
This section describes how to configure basic IPv4 IS-IS functions.
Usage Scenario
To deploy IS-IS on an IPv4 network, configure basic IS-IS functions for communication between different nodes on the network.
Other IS-IS functions can be configured only after basic IS-IS functions are configured.
Create IPv4 IS-IS processes.
Configure IPv4 IS-IS interfaces.
- Creating an IPv4 IS-IS Process
To configure basic IPv4 IS-IS functions, first create an IPv4 IS-IS process and enable IPv4 IS-IS interfaces. - Configuring an IPv4 IS-IS Interface
To configure an interface on an IS-IS device to send Hello packets or flood LSPs, IS-IS must be enabled on this interface. - (Optional) Configuring the costs for IPv4 IS-IS Interfaces
Configuring the IS-IS interface costs can control IS-IS route selection. - (Optional) Configuring IPv4 IS-IS Attributes on Networks of
Different Types
Different IS-IS attributes can be configured for different types of network interfaces. - (Optional) Enabling LSP Fragment Extension on an IPv4 IS-IS
Device
If the LSP capacity is insufficient, newly imported routes and new TLVs fail to be added to LSP fragments. In this case, you can use LSP fragment extension to increase the LSP capacity, restoring the LSP space. When the LSP space is restored, the system automatically attempts to re-add these routes and TLVs to LSP fragments. - (Optional) Enabling the Type-132 TLV in LSPs to Carry the IPv4 Address of Only One IS-IS Interface
To implement interworking between Huawei and non-Huawei devices, you need to enable the type-132 TLV in LSPs to carry the IP address of only one IS-IS interface on the Huawei device. - Verifying the Basic IPv4 IS-IS Configuration
After configuring basic IPv4 IS-IS functions, check information about IS-IS neighbors, interfaces, and routes.
Creating an IPv4 IS-IS Process
To configure basic IPv4 IS-IS functions, first create an IPv4 IS-IS process and enable IPv4 IS-IS interfaces.
Context
(Optional) Configure the level of a device.
Configure the device level based on the network planning. If no device level is configured, IS-IS establishes separate neighbor relationships for Level-1 and Level-2 devices and maintains two identical LSDBs, consuming excessive system resources.
(Optional) Configure IS-IS host name mapping.
After IS-IS host name mapping is configured, a host name rather than the system ID of a device is displayed when you run a display command. This configuration improves the maintainability on an IS-IS network.
(Optional) Enable IS-IS adjacency strict-check.
If both IPv4 and IPv6 run on a network, and the IPv6 topology type of this network is standard or compatible, enable IS-IS adjacency strict-check to ensure that an IS-IS adjacency is established only when both IPv4 and IPv6 go Up. IS-IS adjacency strict-check improves network reliability and prevents traffic losses.
(Optional) Enable the alarm function for the number of LSPs in the LSDB.
An IS-IS-capable router may advertise a large number of LSPs due to an excessive number of external routes received because of incorrect configurations or attack packets. In this situation, you can configure alarm and clear alarm thresholds for the number of LSPs in the LSDB. When the proportion of the number of LSPs to the maximum number of LSPs in the LSDB exceeds the alarm threshold, an alarm is generated; when the proportion of the number of LSPs to the maximum number of LSPs in the LSDB falls below the clear alarm threshold, a clear alarm is generated.
(Optional) Configure IS-IS to add purge originator identification (POI) TLV to purge LSPs.
In most cases, a Purge packet (LSP with Remaining Lifetime 0) does not carry any information about the router that generated the Purge packet. Without such information, troubleshooting is difficult if a network problem occurs. To address this issue, you can configure IS-IS to add POI TLV to purge LSPs. If a dynamic hostname has been configured for the local device, the hostname TLV is also added to the purge LSPs, which facilitates troubleshooting.
(Optional) Disable automatic IS-IS system ID recovery in case of conflicts.
If the same system ID is configured for more than one device on the same network, network flapping may occur.
Procedure
- Create an IS-IS process
and configure the NET of a device.
- (Optional) Configure the
level of a device.
- (Optional) Configure IS-IS
host name mapping.
- (Optional)
Enable IS-IS adjacency strict-check.
- (Optional) Enable the alarm function for the number of LSPs in
the LSDB.
- (Optional) Configure IS-IS to add POI TLV to purge LSPs.
- (Optional) Disable
automatic IS-IS system ID recovery in case of conflicts.
Configuring an IPv4 IS-IS Interface
To configure an interface on an IS-IS device to send Hello packets or flood LSPs, IS-IS must be enabled on this interface.
Context
The level of an IS-IS device and level of an interface determine the level of a neighbor relationship. By default, Level-1 and Level-2 neighbor relationships will be established between two Level-1-2 devices. If only one level of neighbor relationships is required, you can configure the level of an interface to prevent the establishment of neighbor relationships of the other level.
After IS-IS is enabled on an interface, the interface will automatically send Hello packets, attempting to establish neighbor relationships. If a peer device is not an IS-IS device or if an interface is not expected to send Hello packets, suppress the interface. Then this interface only advertises routes of the network segment where the interface resides but does not send Hello packets. This suppression improves the link bandwidth usage.
(Optional) Configuring the costs for IPv4 IS-IS Interfaces
Configuring the IS-IS interface costs can control IS-IS route selection.
Context
The link cost of an IS-IS interface can be an interface cost, global cost, or automatically calculated cost which take effect in descending order.
The interface cost takes effect only on a specified interface.
The global cost takes effect only on all interfaces.
The automatically calculated cost is a cost automatically calculated based on the interface bandwidth.
The default cost of an IS-IS interface is 10, and the default cost style is narrow.
(Optional) Configuring IPv4 IS-IS Attributes on Networks of Different Types
Different IS-IS attributes can be configured for different types of network interfaces.
Context
The establishment mode of IS-IS neighbor relationships on a broadcast network is different from that on a P2P network. Different IS-IS attributes can be configured for interfaces on different types of networks.
IS-IS is required to select a DIS on a broadcast network. Configure the DIS priorities of IS-IS interfaces so that the interface with the highest priority is selected as the DIS.
The network types of the IS-IS interfaces on both ends of a link must be the same, otherwise, the IS-IS neighbor relationship cannot be established between the two interfaces. If the type of an interface on the neighbor is P2P, you can configure the interface type on the local device to P2P so that an IS-IS neighbor relationship can be established between the two devices.
IS-IS on a P2P network is not required to select a DIS. Therefore, you do not need to configure DIS priorities. To ensure the reliability of P2P links, configure IS-IS to use the three-way handshake mode for IS-IS neighbor relationship establishment so that faults on a unidirectional link can be detected.
Procedure
- Configure the DIS priority of an IS-IS interface.
- Configure the network type of an IS-IS interface.
- Set the negotiation mode for the establishment
of neighbor relationships.
- Configure OSICP negotiation check on PPP
interfaces.
- Configure the scale of the Hello packets sent on the IS-IS
interface.
- Prevent IS-IS from checking whether the IP addresses of
received Hello packets are on the same network segment.
(Optional) Enabling LSP Fragment Extension on an IPv4 IS-IS Device
If the LSP capacity is insufficient, newly imported routes and new TLVs fail to be added to LSP fragments. In this case, you can use LSP fragment extension to increase the LSP capacity, restoring the LSP space. When the LSP space is restored, the system automatically attempts to re-add these routes and TLVs to LSP fragments.
Context
The lsp-fragments-extend command enables LSP fragment extension on an IS-IS device in a specified mode and at a specified level. One LSP fragment occupies only one byte and therefore a maximum of 256 fragments are supported. If there are a great number of LSPs and the number of fragments exceeds 256, some information is lost. LSP fragment extension is introduced to address such a problem. You can run the virtual-system command to configure one or more virtual systems to support more than 256 LSP fragments.
Procedure
- Run system-view
The system view is displayed.
- Run isis [ process-id ]
An IS-IS process is created, and the IS-IS process view is displayed.
- Run lsp-fragments-extend [ [ level-1 | level-2 | level-1-2 ] | [ mode-1 | mode-2 ] ] *
LSP fragment extension is enabled on an IS-IS device, and a specified mode and level are specified.
(Optional) Enabling the Type-132 TLV in LSPs to Carry the IPv4 Address of Only One IS-IS Interface
To implement interworking between Huawei and non-Huawei devices, you need to enable the type-132 TLV in LSPs to carry the IP address of only one IS-IS interface on the Huawei device.
Context
By default, on Huawei devices, the type-132 TLV in LSPs carries the IP addresses of all IS-IS interfaces. However, on some non-Huawei devices, the type-132 TLV in LSPs carries the IP address of only one IS-IS interface. To implement interworking between Huawei devices and these non-Huawei devices, enable the type-132 TLV in LSPs to carry the IP address of only one IS-IS interface on the Huawei devices.
Procedure
- Run system-view
The system view is displayed.
- Run isis [ process-id ]
An IS-IS process is created, and its view is displayed.
- Run advertise one-interface-address
The type-132 TLV in LSPs is enabled to carry the IP address of only one IS-IS interface.
- Run commit
The configuration is committed.
Verifying the Basic IPv4 IS-IS Configuration
After configuring basic IPv4 IS-IS functions, check information about IS-IS neighbors, interfaces, and routes.
Procedure
- Run the display isis name-table [ process-id | vpn-instance vpn-instance-name ] command to check the mapping from the name of the local device to the system ID.
- Run the display isis peer [ verbose ] [ process-id | vpn-instance vpn-instance-name ] command to check information about IS-IS neighbors.
- Run the display isis interface [ verbose ] [ process-id | vpn-instance vpn-instance-name ] command to check information about IS-IS interfaces.
- Run the display isis route [ process-id | vpn-instance vpn-instance-name ] [ ipv4 ] [ verbose | [ level-1 | level-2 ] | ip-address [ mask | mask-length ] ] * command to check information about IS-IS routes.
Example
Run the display isis name-table command to view the mappings between host names and system IDs.
<HUAWEI> display isis name-table Name table information for ISIS(1) Level-1 System ID Hostname Type ------------------------------------------------------------------------------- 1111.1111.1111 DeviceA DYNAMIC 2222.2222.2222 DeviceB DYNAMIC
Run the display isis peer command. The command output shows the status of an IS-IS neighbor, DeviceB. System Id is displayed as DeviceB.
<HUAWEI> display isis peer
Run the display isis interface verbose command to view information about IS-IS interfaces. The command output shows that the DIS status of a broadcast interface is Yes, the priority of the DIS is 20, and that the cost of the interface is 30.
<HUAWEI> display isis interface verbose Suppress Base : NO IPv6 Suppress Base : NO Extended-Circuit-Id Value : 0000000000 Circuit State : OSI:UP / IP:UP / MTU:UP / IPBorrow:UP / BandWidth:UP / IsEnable:UP / Interface:UP Circuit Ipv6 State : OSI:UP / IP:UP / MTU:UP / IPBorrow:UP / BandWidth:UP / IsEnable:DOWN / Interface:UP
Run the display isis route command to view information about IS-IS routes. The command output shows a route with destination network segment 12.1.1.0/24 and next hop address 23.1.1.0/24.
<HUAWEI> display isis route Route information for ISIS(1) ----------------------------- ISIS(1) Level-2 Forwarding Table -------------------------------- IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags ------------------------------------------------------------------------------- 12.1.1.0/24 40 NULL GE1/0/2 23.1.1.1 A/-/-/- 23.1.1.0/24 10 NULL GE1/0/2 Direct D/-/L/- Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut, U-Up/Down Bit Set