cerc-io
/
stack-orchestrator
mirror of https://github.com/cerc-io/stack-orchestrator
1
0
Fork 0
Code Issues Actions Packages Projects Releases Wiki Activity
stack-orchestrator/docs/arista-scraped/nexthop-groups.md

29 KiB
Raw Blame History

Nexthop Groups

These sections describe the Nexthop groups:

  • Next-hop Group Description

  • Next-hop Group Configuration

  • Nexthop Group commands

Next-hop Group Description

Each routing table entry provides the next hop address to a specified destination. A next-hop address consists of the address of the next device on the path to the entry specified destination.

A next-hop group uses a data structure that defines a list of next-hop addresses and a tunnel type for packets routed to the specified address. When an IP route statement specifies a next-hop group as the next-hop address, the switch configures a static route with a next-hop group member as the next-hop address and encapsulates packets forwarded to that address as required by the group tunnel type.

Configure the next-hop group size as a parameter that specifies the number of entries that the group contains. Group entries not explicitly configured are filled with drop routes. The switch uses ECMP hashing to select the address within the next-hop group when forwarding packets. When a packet’s hash selects a drop route, the switch drops the packet.

Next-hop groups are supported on Trident platform switches and has the following restrictions:

  • Each switch can support 512 IPv4 or IPv6 Tunnels

  • Next-hop groups can contain 256 next-hops.

  • The switch supports 1024 next-hop groups.

  • Multiple routes can share a tunnel.

  • Tunnels do not support IP multicast packets.

Next-hop groups support IP-in-IP tunnels. The entry IP address family within a particular next-hop group cannot be mixed. They must be all IPv4 or all IPv6 entries.

Next-hop Group Configuration

Next-hop groups are configured and modified in next-hop-group configuration mode. After a group is created, it is associated to a static route through an ip route nexthop-group statement.

These tasks are required to configure a next-hop group and apply it to a static route.

  • Creating and Editing Next-hop Groups

  • Configuring a Group’s Encapsulation Parameters

  • Configuring the Group’s Size

  • Creating Next-hop Group Entries

  • Displaying Next-hop Groups

  • Applying a Next-hop Group to a Static Route

Creating and Editing Next-hop Groups

Create next-hop groups using the nexthop-group command that specifies an unconfigured group. The switch enters nexthop-group configuration mode for the new group. Nexthop-group mode is also accessible for modifying existing groups. When in nexthop-group configuration mode, the show active command displays the group’s configuration.

  • This command creates a next-hop group named NH-1.
`switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)#`
  • These commands enter nexthop-group configuration mode for the group named NH3, then displays the previously configured group parameters.
`switch(config)# **nexthop-group NH3**
switch(config-nexthop-group-NH3)#show active
 nexthop-group NH3
   size 4
   ttl 10
   entry 0 tunnel-destination 10.14.21.3
   entry 1 tunnel-destination 10.14.21.5
   entry 2 tunnel-destination 10.14.22.5
   entry 3 tunnel-destination 10.14.22.6
switch(config-nexthop-group-NH3)#`

Configuring Group Encapsulation Parameters

Packets in static routes associated with the next-hop group are encapsulated to support the group’s tunnel type. Nexthop groups support IP-in-IP tunnels. The group also defines the source IP address and TTL field contents included in the packet encapsulation.

  • This command configures the TTL setting to 32 for nexthop group NH-1 encapsulation packets.
`switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **ttl 32**
switch(config-nexthop-group-NH-1)# **show active**
 nexthop-group NH-1
   size 128
   ttl 32
switch(config-nexthop-group-NH-1)#`

The address is inserted in the encapsulation source IP fields is specified by tunnel-source (Next-hop Group).

  • These commands create interface loopback 100, assign an IP address to the interface, then specifies that address as the tunnel source for packets designated by next-hop-group NH-1.
`switch(config)# **interface loopback 100**
switch(config-if-Lo100)# **ip address 10.1.1.1/32**
switch(config-if-Lo100)# **exit**
switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **tunnel-source intf loopback 100**
switch(config-nexthop-group-NH-1)# **show active**
 nexthop-group NH-1
   size 256
   ttl 32
   tunnel-source intf Loopback100
switch(config-nexthop-group-NH-1)#`

Configure the nexthop group tunnel to become active in the tunnel RIB only if a viable nexthop group exists. A nexthop group becomes viable when it meets specific reachability and programming criteria determined by one or more underlying entries resolving in the Forwarding Information Base (FIB) and has programmability. By default, IP tunnels become active even if no viable nexthop group exists. To override this behavior, use the following commands:

`switch(config)# **router general**
switch(config-router-general)# **tunnel nexthop-group unresolved invalid**
switch(config-router-general)#`

Configuring IP-in-IP Encapsulation

Through IP-in-IP encapsulation, IP packets matching a static Nexthop-Group route encapsulate within an IP-in-IP tunnel and forward.

This command configures a static Nexthop-Group route and an IP-in-IP Nexthop-Group for IP-in-IP encapsulation.

`switch(config)# **ip route 124.0.0.1/32 nexthop-group abc**
switch(config)# **nexthop-group abc type ip-in-ip**
switch(config-nexthop-group-abc)# **size 512**
switch(config-nexthop-group-abc)# **tunnel-source 1.1.1.1**
switch(config-nexthop-group-abc)# **entry 0 tunnel-destination 1.1.1.2**
switch(config-nexthop-group-abc)# **entry 1 tunnel-destination 10.1.1.1**
switch(config-nexthop-group-abc)# **ttl 64**
switch(config-nexthop-group-abc)#`

Configuring the Group’s Size

The group’s size specifies the number of entries in the group. A group can contain up to 256 entries, which is the default size. The group’s size is specified by size (Nexthop Group).

This command configures the next-hop group NH-1 to contain 128 entries.

`switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **size 128**
switch(config-nexthop-group-NH-1)# **show active**
 nexthop-group NH-1
   size 128
   ttl 64
switch(config-nexthop-group-NH-1)#`

Creating Next-hop Group Entries

Each entry specifies a next-hop address that is used to forward packets. A next-hop group contains one entry statement for each next-hop address. The group size specifies the number of entry statements the group may contain. Each entry statement is assigned an index number to distinguish it from other entries within the group, and entry index numbers range from zero to the group size minus one.

Next-hop group entries are configured by entry (Next-hop Group).

  • These commands set the next-hop group size at four entries, then create three entries. eos drops packets hashed to the fourth entry.
`switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **size 4**
switch(config-nexthop-group-NH-1)# **entry 0 tunnel-destination 10.13.4.4**
switch(config-nexthop-group-NH-1)# **entry 1 tunnel-destination 10.15.4.22**
switch(config-nexthop-group-NH-1)# **entry 2 tunnel-destination 10.15.5.37**
switch(config-nexthop-group-NH-1)# **show active**
 nexthop-group NH-1
   size 4
   ttl 64
   entry 0 tunnel-destination 10.13.4.4
   entry 1 tunnel-destination 10.15.4.22
   entry 2 tunnel-destination 10.15.5.37
switch(config-nexthop-group-NH-1)#`
  • These commands configure a next-hop group with three IPv6 next-hop entries.
`switch(config)# **nexthop-group nhg-v6-mpls type ip**
switch(config-nhg-v6-mpls)# **size 3**
switch(config-nhg-v6-mpls)# **entry 0 nexthop 2002::6401:1**
switch(config-nhg-v6-mpls)# **entry 1 nexthop 2002::6404:1**
switch(config-nhg-v6-mpls)# **entry 2 nexthop 2002::6404:2**
switch(config-nhg-v6-mpls)#`
  • These commands configure an IPv4 route to point to the next-hop group nhg-v6-mpls. (Both IPv4 routes and IPv6 routes can point to this next-hop group.)
`switch# **ip route 100.5.0.0/16 Nexthop-Group nhg-v6-mplsp**
switch#`

Displaying Next-hop Groups

The show nexthop-group command displays a group configured parameters.

This command displays the properties of the nexthop group named NH-1.

`switch> **show nexthop-group NH-1**
Name             Id       type     size   ttl    sourceIp
NH-1             4        ipInIp   256    64     0.0.0.0
switch>`

Applying a Next-hop Group to a Static Route

The ip route nexthop-group associates a next-hop group with a specified destination address and configures the encapsulation method for packets tunneled to that address.

This command creates a static route in the default VRF, using the next-hop group of NH-1 to determine the next hop address.

`switch(config)# **ip route 10.17.252.0/24 nexthop-group NH-1**
switch(config)#`

The show ip route command displays the routing table for a specified VRF. Routes that utilize a next-hop group entry are noted with a route type code of NG.

This command displays a routing table that contains a static route with its next-hop specified by a next-hop group.

`switch> **show ip route**
Codes: C - connected, S - static, K - kernel,
       O - OSPF, IA - OSPF inter area, E1 - OSPF external type 1,
       E2 - OSPF external type 2, N1 - OSPF NSSA external type 1,
       N2 - OSPF NSSA external type2, B I - ibgp, B E - ebgp,
       R - RIP, I - ISIS, A B - bgp Aggregate, A O - OSPF Summary,
       NG - Nexthop Group Static Route

Gateway of last resort is not set

 C      10.3.3.1/32 is directly connected, Loopback0
 C      10.9.1.0/24 is directly connected, Ethernet51/3
 C      10.10.10.0/24 is directly connected, Ethernet51/1
 S      10.20.0.0/16 [20/0] via 10.10.10.13, Ethernet51/1
 C      10.10.11.0/24 is directly connected, Ethernet3
 NG     10.10.3.0/24 [1/0] via ng-test1, 5
 C      10.17.0.0/20 is directly connected, Management1
 S      10.17.0.0/16 [1/0] via 10.17.0.1, Management1
 S      10.18.0.0/16 [1/0] via 10.17.0.1, Management1
 S      10.19.0.0/16 [1/0] via 10.17.0.1, Management1
 S      10.20.0.0/16 [1/0] via 10.17.0.1, Management1
 S      10.22.0.0/16 [1/0] via 10.17.0.1, Management1

switch>`

Support for IPv6 Link-Local Addresses in Next-hop Groups Entries

IPv6 Link-local addresses in Next-hop Groups entries support IPv6 link-local next-hops belonging to a Next-hop Group. Only the MPLS Next-hop Group supports IPv6 and because of this, IPv6 is limited to getting support only by the Nexthop Group of MPLS. An advantage is that you can use these devices even when they are not configured with globally routable IPv4 or IPv6 addresses.

Configuration

An MPLS next-hop group with IPv6 address now accepts an interface if the IPv6 address is a link-local. Note the use of percentages between the IPv6 address and the interface.

`switch(config)# **nexthop-group nhg1 type mpls**
switch(config-nexthop-group-nhg1)# **entry 0 push label-stack 606789 nexthop fe80::fe80:2%Ethernet2**
switch(config-nexthop-group-nhg1)# **entry 1 push label-stack 204164 nexthop fe80::fe80:2%Ethernet3**`

Show commands

Use the show nexthop-group command to display the current status of the nexthop-groups.

`switch# **show nexthop-group**
nhg1
  Id                1
  Type              mpls
  Size              12
  Entries (left most label is the top of the stack)
    0  push label-stack 606789   nexthop fe80::fe80:2
         Tunnel destination directly connected, Ethernet2
         00:d4:27:77:e9:77, Ethernet2
    1  push label-stack 204164   nexthop fe80::fe80:2
         Tunnel destination directly connected, Ethernet3
         00:79:21:32:0f:32, Ethernet3`

Limitations

Review the following limitations for the support of IPv6 link-local address in nexthop group entries:

  • Only the nexthop-group of MPLS supports an IPv6 address. Therefore, link-local IPv6 addresses are only supported for this type of nexthop-group.

  • Nexthop-groups are configured and exist in the default VRF. The link-local IPv6 addresses for nexthop-group entries can only be resolved for interfaces in the default VRF.

Nexthop Group commands

Nexthop commands

  • entry (Next-hop Group)

  • ip route nexthop-group

  • nexthop-group

  • size (Nexthop Group)

  • ttl (Next-hop Group)

  • tunnel-source (Next-hop Group)

Nexthop Show Command

  • show nexthop-group

entry (Next-hop Group)

The entry command defines a next-hop entry in the nexthop group configuration mode . Each next-hop entry specifies a next-hop IP address for static routes to which the next-hop group is assigned. The group size (size (Nexthop Group)) specifies the quantity of entries a group contains. Each entry is created by an individual command. Entries within a group are distinguished by an index number.

The no entry and default entry commands delete the specified nexthop group entry, as referenced by index number, by removing the corresponding entry statement from running-config.

Command Mode

Nexthop-group Configuration

Command Syntax

entry index tunnel-destination ipv4_address

no entry index

default entry index

Parameters

  • index - Entry index. Values range from 0 to group-size – 1.

  • ipv4_address - Nexthop IPv4 address.

  • group-size - the group’s entry capacity as specified by the size (Nexthop Group) command.

Example

These commands sets the next-hop group size at four entries, then creates three next-hop entries. eos drops packets hashed to the fourth entry.

`switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **size 4**
switch(config-nexthop-group-NH-1)# **entry 0 tunnel-destination 10.13.4.4**
switch(config-nexthop-group-NH-1)# **entry 1 tunnel-destination 10.15.4.22**
switch(config-nexthop-group-NH-1)# **entry 2 tunnel-destination 10.15.5.37**
switch(config-nexthop-group-NH-1)# **show active**
 nexthop-group NH-1
   size 4
   ttl 64
   entry 0 tunnel-destination 10.13.4.4
   entry 1 tunnel-destination 10.15.4.22
   entry 2 tunnel-destination 10.15.5.37
switch(config-nexthop-group-NH-1)#`

ip route nexthop-group

The ip route nexthop-group command creates a static route. The destination is a network segment. The next-hop address is one of the IP addresses that comprise the specified next-hop group. Packets forwarded as a result of this command are encapsulated as specified by the tunnel-type parameter of the specified next-hop group.

When multiple routes exist to a destination prefix, the route with the lowest administrative distance takes precedence. When a route created through this command has the same administrative distance as another static route (ECMP), the route that was created earliest has preference; running-config stores static routes in the order that they are created.

By default, the administrative distance assigned to static routes is 1. Assigning a higher administrative distance to a static route configures it to be overridden by dynamic routing data. For example, a static route with a distance value of 200 is overridden by OSPF intra-area routes, which have a default distance of 110.

The no ip route nexthop-group and default ip route nexthop-group commands delete the specified route by removing the corresponding ip route nexthop-group command from running-config. ip route nexthop-group statements for an IP address in multiple VRFs must be removed separately.

A no ip route or default ip route command without a next-hop parameter deletes all corresponding ip route nexthop-group statements. Deleting a user-defined VRF also deletes its static routes.

Command Mode

Global Configuration

Command Syntax

ip route [VRF_INST dest_net nexthop-group nhgp_name [dist][TAG_OPTION][RT_NAME]

no ip route [VRF_INST] dest_net [nexthop-group nhgroup_name][distance]

default ip route [VRF_INST] dest_net [nexthop-group nhgroup_name][distance]

Parameters

  • VRF_INST      Specifies the VRF instance being modified.

  • no parameter      Changes are made to the default VRF.

  • vrf vrf_name      Changes are made to the specified VRF.

  • dest_net      Destination IPv4 subnet (CIDR or address-mask notation).

  • nhgp_name      Name of next-hop group.

  • dist Administrative distance assigned to route. Options include:

  • no parameter      Route assigned default administrative distance of one.

  • 1-255      The administrative distance assigned to route.

  • TAG_OPTION      Static route tag. Options include:

  • no parameter      Assigns default static route tag of 0.

  • tag t_value       Static route tag value. t_value ranges from 0 to 4294967295.

  • RT_NAME       Associates descriptive text to the route. Options include:

  • no parameter       No text is associated with the route.

  • name descriptive_text      The specified text is assigned to the route.

Related commands

The ip route command creates a static route that specifies the next-hop address without using next-hop groups.

Example

This command creates a static route in the default VRF, using the next-hop group of NH-1 to determine the next hop address.

`switch(config)# **ip route 10.17.252.0/24 nexthop-group NH-1**
switch(config)#`

nexthop-group

The nexthop-group command places the switch in nexthop-group configuration mode, through which next-hop groups are created or modified. The command also specifies the tunnel protocol for extracting payload from encapsulated packets that arrive through an IP address upon which the group is applied.

A next-hop group is a data structure that defines a list of next-hop addresses and the encapsulation process for packets routed to the specified address. The command either accesses an existing nexthop group configuration or creates a new group if it specifies a non-existent group. Supported tunnel protocols include IP ECMP and IP-in-IP.

The nexthop-group configuration mode is not a group change mode; running-config is changed immediately upon entering commands. Exiting the nexthop-group configuration mode does not affect running-config. The exit command returns the switch to global configuration mode.

The no nexthop-group and default nexthop-groupcommands delete previously configured commands in the specified nexthop-group mode. When the command does not specify a group, it removes all next-hop-groups. When the command specifies a tunnel type without naming a group, it removes all next-hop-groups of the specified type.

Command Mode

Global Configuration

Command Syntax

nexthop-group group_name type TUNNEL_TYPE

no nexthop-group [group_name][type TUNNEL_TYPE]

default nexthop-group [group_name][typeTUNNEL_TYPE]

Parameters

  • group_name Nexthop group name.

  • TUNNEL_TYPE Tunnel protocol of the nexthop-group. Options include:

  • ip ECMP nexthop.

  • ip-in-ip IP in IP tunnel.

  • gre Encapsules the Layer 3 protocols overs IP networks.

  • mpls-over-gre Tunnels MPLS over a non-MPLS network.

  • entry Nexthop Group Entry Configuration.

  • size Nexthop Group Entry Size.

  • tos Tunnel encapsulation IP type of service.

  • ttl Tunnel encapsulation TTL value.

  • tunnel-source Source Interface or Address.

commands Available in Nexthop-group Configuration Mode

  • entry (Next-hop Group)

  • size (Nexthop Group)

  • ttl (Next-hop Group)

  • tunnel-source (Next-hop Group)

Restrictions

Tunnel type availability varies by switch platform.

Examples

  • This command creates a nexthop group named NH-1 that specifies ECMP nexthops.
`switch(config)# **nexthop-group NH-1 type ip**
switch(config-nexthop-group-NH-1)#`
  • This command exits nexthop-group mode for the NH-1 nexthop group.
`switch(config-nexthop-group-NH-1)# **exit**
switch(config)#`
  • These commands creates a nexthop group NH-2 of type MPLS over GRE.
`switch(config)# **nexthop-group NH-2 type mpls-over-gre**
switch(config-nexthop-group-NH-2)# **tunnel-source 11.1.1.1**
switch(config-nexthop-group-NH-2)# **ttl 32**
switch(config-nexthop-group-NH-2)# **tos 20**
switch(config-nexthop-group-NH-2)# **entry 0 push label-stack 16000 tunnel-destination 11.1.1.2**
switch(config)# **ip route 100.1.1.1/32 Nexthop-Group NH-2**

Counters for nexthop group may be enabled using the following command
switch(config)# **hardware counter feature nexthop**`

show nexthop-group

The show nexthop-group command displays properties of the specified nexthop group.

Command Mode

EXEC

Command Syntax

show nexthop-group nhgroup_name [VRF_INST]

Parameters

  • nhgroup_name Name of the group displayed by command.

  • VRF_INST Specifies the VRF instance for which data is displayed.

  • no parameter     Context-active VRF.

  • vrf vrf_name Specifies the name of VRF instance. System default VRF is specified by default.

Related commands

The show nexthop-group command places the switch in the nexthop-group configuration mode to create a new group or modify an existing group.

Example

This command displays the nexthop group information.

`switch(config)# **show nexthop-group**
  Id         107
  Type       mplsOverGre
  Size       1  (auto size enabled, programmed size 1)
  TTL        32
  Source IP  11.1.1.1
  Entries (left most label is the top of the stack)
    0  push label-stack 16000   tunnel-destination 11.1.1.2
         Tunnel destination directly connected, Ethernet1
         00:00:aa:aa:aa:aa, Ethernet1

With nexthop group counter enabled
switch(config)# **show nexthop-group**
  Id         1
  Type       mplsOverGre
  Size       1  (auto size enabled, programmed size 1)
  TTL        64
  Source IP  0.0.0.0
  Entries (left most label is the top of the stack)
    0  push label-stack 16000   tunnel-destination 1.1.1.2
         Tunnel destination directly connected, Ethernet1
         00:00:aa:aa:aa:aa, Ethernet1
         0 packets, 0 bytes

switch(config)#**show nexthop-group summary**
Number of Nexthop Groups configured: 1
Number of unprogrammed Nexthop Groups: 0

  Nexthop Group Type   Configured
-------------------- ------------
       MPLS over GRE            1

  Nexthop Group Size   Configured
-------------------- ------------
                   1            1`

size (Nexthop Group)

The size command configures the quantity of next-hop entries in the Nexthop-Group Configuration Mode . Each entry specifies a next-hop IP address for static routes to assign to the group. Configure entries with the entry (Next-hop Group) command. The default size is 256 entries.

The no size and default size commands restore the size of the configuration mode nexthop group to the default value of 256 by removing the corresponding size command from running-config.

Command Mode

Nexthop-group Configuration

Command Syntax

size entry_size

no size entry_size

default size entry_size

Parameter

entry_size Group size (entries). Value ranges from 1 to 255 with a default value of 256.

Example

This command configures the next-hop group NH-1 to contain 128 entries.

`switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **size 128**
switch(config-nexthop-group-NH-1)# **show active**
 nexthop-group NH-1
   size 128
   ttl 64
switch(config-nexthop-group-NH-1)#`

ttl (Next-hop Group)

The ttl command specifies the number entered into the TTL (time to live) encapsulation field of packets transmitted to the address designated by the configuration mode next-hop group. The default TTL value is 64.

The no ttl and default ttl commands restore the default TTL value written into TTL fields for the nexthop group configuration mode by deleting the corresponding ttl command from running-config.

Command Mode

Nexthop-group Configuration

Command Syntax

ttl hop_expiry

no ttl hop_expiry

default ttl hop_expiry

Parameters

hop_expiry     Period that the packet remains valid (seconds or hops) Value ranges from 1 to 64.

Restrictions

This command is available only to Next-hop groups for tunnels of type IP-in-IP, GRE, MPLS, and MPLS over GRE.

Related commands

The nexthop-group command places the switch in the nexthop-group configuration mode.

Examples

  • This command configures the ttl setting to 32 for next-hop group NH-1 packets.
`switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **ttl 32**
switch(config-nexthop-group-NH-1)# **show active**
 nexthop-group NH-1
   size 128
   ttl 32
switch(config-nexthop-group-NH-1)#`
  • This command restores the no ttl setting for next-hop group NH-1 packets.
`switch(config-nexthop-group-NH-1)# **no ttl**
switch(config-nexthop-group-NH-1)# **show active nexthop-group NH-1**
   size 128
   ttl 64
switch(config-nexthop-group-NH-1)#`

tunnel-source (Next-hop Group)

The tunnel-source command specifies the address that is entered into the source IP address encapsulation field of packets that are transmitted as designated by the nexthop group configuration mode . The command may directly specify an IP address or specify an interface from which an IP address is derived. The default source address IP address is 0.0.0.0.

The no tunnel-source and default tunnel-source commands remove the source IP address setting from the configuration mode nexthop group by deleting the tunnel-source command from running-config.

Command Mode

Nexthop-group Configuration

Command Syntax

tunnel-source SOURCE

no tunnel-source SOURCE

default tunnel-source SOURCE

Parameters

SOURCE IP address or derivation interface. Options include:

  • ipv4_addr      An IPv4 address.

  • intf ethernet e_num     Ethernet interface specified by e_num.

  • intf loopback l_num     Loopback interface specified by l_num.

  • intf management m_num     Management interface specified by m_num.

  • intf port-channel p_num     Port-channel interface specified by p_num.

  • intf vlan v_num     VLAN interface specified by v_num.

Restrictions

This command is available only to Nexthop groups for tunnels of type ip-in-ip.

Related commands

The nexthop-group command places the switch in the nexthop-group configuration mode.

Example

These commands create interface loopback 100, assign an IP address to the interface, then specifies that address as the tunnel source for packets designated by nexthop-group NH-1.

`switch(config)# **interface loopback 100**
switch(config-if-Lo100)# **ip address 10.1.1.1/32**
switch(config-if-Lo100)# **exit**

switch(config)# **nexthop-group NH-1**
switch(config-nexthop-group-NH-1)# **tunnel-source intf loopback 100**
switch(config-nexthop-group-NH-1)# **show active nexthop-group NH-1**
   size 256
   ttl 64
   tunnel-source intf Loopback100
switch(config-nexthop-group-NH-1)# **show nexthop-group NH-1**
Name             Id       type     size   ttl    sourceIp
NH-1             2        ipInIp   256    64     10.1.1.1

switch(config-nexthop-group-NH-1)#`

tunnel nexthop-group unresolved

The tunnel nexthop-group unresolved command in the Router General Configuration Mode installs a nexthop-group tunnel only if a viable nexthop group exists. Using this command overrides the default behavior of creating a nexthop-group tunnel even if no viable nexthop-group exists for the configuration.

The no | default versions of the command removes the configuration from the running-config on the switch.

Command Mode

Router General Configuration

Command Syntax

tunnel nexthop-group unresolved invalid

no tunnel nexthop-group unresolved invalid

default tunnel nexthop-group unresolved invalid

Parameters

  • tunnel - Specifies using a tunnel for the configuration.

  • nexthop-group - Applies the configuration to nexthop groups.

  • unresolved - Specifies applying the command to unreachable destinations.

  • invalid - Do not install the tunnel in the routing table.

Example

Use the following commands to apply the configuration to the switch:

`switch(config)# **router general**
switch(config-router-general)# **tunnel nexthop-group unresolved invalid**
switch(config-router-general)`