Published On: August 6ᵗʰ, 2019 02:02

Cisco TrustSec Configuration Guide, Cisco IOS XE Release 3S

Subnet to security group tag (SGT) mapping binds an SGT to all host addresses of a specified subnet. Once this mapping is implemented, Cisco TrustSec imposes the SGT on any incoming packet that has a source IP address which belongs to the specified subnet.

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Restrictions for Cisco TrustSec Subnet to SGT Mapping

  • An IPv4 subnetwork with a /31 prefix cannot be expanded.

  • Subnet host addresses cannot be bound to SGTs when the cts sxp mapping network-map command bindings argument is less than the total number of subnet hosts in the specified subnets or when the number of bindings is 0.

  • IPv6 expansions and propagation only occurs when SXP speaker and listener are running SXPv3, or more recent versions.

Information About Cisco TrustSec Subnet to SGT Mapping

In IPv4 networks, SXPv3, and more recent versions, can receive and parse subnet network address/prefix strings from SXPv3 peers. Earlier SXP versions convert the subnet prefix into its set of host bindings before exporting them to an SXP listener peer.

For example, the IPv4 subnet 198.1.1.0/29 is expanded as follows (only 3 bits for host addresses):
  • Host addresses 198.1.1.1 to 198.1.1.7 are tagged and propagated to SXP peer.

  • Network and broadcast addresses 198.1.1.0 and 198.1.1.8 are not tagged and not propagated.


Note


To limit the number of subnet bindings SXPv3 can export, use the cts sxp mapping network-map global configuration command.


Subnet bindings are static, which means that active hosts are not learned. They can be used locally for SGT imposition and SGACL enforcement. Packets tagged by subnet to SGT mapping can be propagated on Layer 2 or Layer 3 TrustSec links.

Note


For IPv6 networks, SXPv3 cannot export subnet bindings to SXPv2 or SXPv1 peers.


How to Configure Cisco TrustSec Subnet to SGT Mapping

Configuring Subnet to SGT Mapping

SUMMARY STEPS

1. enable

2. configure terminal

3. cts sxp mapping network-map bindings

4. cts role-based sgt-map ipv4-address sgt number

5. cts role-based sgt-map ipv6-address::prefix sgt number

6. exit

7. show running-config | include search-string

8. show cts sxp connections

9. show cts sxp sgt-map

10. copy running-config startup-config


DETAILED STEPS
  Command or Action Purpose
Step 1 enable


Example:
Device> enable
 

Enables privileged EXEC mode.

  • Enter your password if prompted.

 
Step 2 configure terminal


Example:
Device# configure terminal
 

Enters global configuration mode.

 
Step 3 cts sxp mapping network-map bindings


Example:
Device(config)# cts sxp mapping network-map 10000
 

Configures the subnet to SGT mapping host count constraint. The bindings argument specifies the maximum number of subnet IP hosts from 0 to 65,535 that can be bound to SGTs and exported to the SXP listener. The default is 0 (no expansions performed).

 
Step 4 cts role-based sgt-map ipv4-address sgt number


Example:
Device(config)# cts role-based sgt-map 10.10.10.10/29 sgt 1234
 

(IPv4) Specifies an IPv4 subnet in CIDR notation.

The number of bindings specified in step 3 should match or exceed the number of host addresses in the subnet (excluding network and broadcast addresses). The sgt number keyword pair specifies the SGT number that is to be bound to every host address in the specified subnet.

  • ipv4-address—Specifies the IPv4 network address in dotted decimal notation.

  • prefix—(0 to 30). Specifies the number of bits in the network address.

  • sgt number (0-65,535). Specifies the SGT number.

 
Step 5 cts role-based sgt-map ipv6-address::prefix sgt number


Example:
Device(config)# cts role-based sgt-map 2020::/64 sgt 1234
 

(IPv6) Specifies an IPv6 subnet in hexadecimal notation.

The number of bindings specified in step 3 should match or exceed the number of host addresses in the subnet (excluding network and broadcast addresses). The sgt number keyword pair specifies the SGT number that is to be bound to every host address in the specified subnet.

  • ipv6-address—Specifies the IPv4 network address in dotted decimal notation.

  • prefix—(0 to 30). Specifies the number of bits in the network address.

  • sgt number—(0-65,535). Specifies the SGT number.

 
Step 6 exit


Example:
Device(config)# exit
 

Exits global configuration mode.

 
Step 7 show running-config | include search-string


Example:
Device# show running-config | include sgt 1234
Device# show running-config | include network-map
 

Verifies that the cts role-based sgt-map and the cts sxp mapping network-map commands are in the running configuration.

 
Step 8 show cts sxp connections


Example:
Device# show cts sxp connections
 

Displays the SXP speaker and listener connections with their operational status.

 
Step 9 show cts sxp sgt-map


Example:
Device# show cts sxp sgt-map
 

Displays the IP to SGT bindings exported to the SXP listeners.

 
Step 10 copy running-config startup-config


Example:
Device# copy running-config startup-config
 

Copies the running configuration to the startup configuration.

 

Cisco TrustSec Subnet to SGT Mapping: Examples

The following example shows how to configure IPv4 Subnet to SGT Mapping between two devices running SXPv3 (Device 1 and Device 2):

Configure SXP speaker/listener peering between Device 1 (10.1.1.1) and Device 2 (10.2.2.2).

Device1# configure terminal
Device1(config)# cts sxp enable
Device1(config)# cts sxp default source-ip 10.1.1.1
Device1(config)# cts sxp default password 1syzygy1
Device1(config)# cts sxp connection peer 10.2.2.2 password default mode local speaker

Configure Device 2 as SXP listener of Device 1.

Device2(config)# cts sxp enable
Device2(config)# cts sxp default source-ip 10.2.2.2
Device2(config)# cts sxp default password 1syzygy1
Device2(config)# cts sxp connection peer 10.1.1.1 password default mode local listener

On Device 2, verify that the SXP connection is operating:

Device2# show cts sxp connections brief | include 10.1.1.1

     10.1.1.1          10.2.2.2          On                3:22:23:18 (dd:hr:mm:sec)

Configure the subnetworks to be expanded on Device 1.

Device1(config)# cts sxp mapping network-map 10000
Device1(config)# cts role-based sgt-map 10.10.10.0/30 sgt 101
Device1(config)# cts role-based sgt-map 10.11.11.0/29 sgt 11111    
Device1(config)# cts role-based sgt-map 172.168.1.0/28 sgt 65000

On Device 2, verify the subnet to SGT expansion from Device 1. There should be two expansions for the 10.10.10.0/30 subnetwork, six expansions for the 10.11.11.0/29 subnetwork, and 14 expansions for the 172.168.1.0/28 subnetwork.

Device2# show cts sxp sgt-map brief | include 101|11111|65000

IPv4,SGT: <10.10.10.1 , 101>
IPv4,SGT: <10.10.10.2 , 101>
IPv4,SGT: <10.11.11.1 , 11111>
IPv4,SGT: <10.11.11.2 , 11111>
IPv4,SGT: <10.11.11.3 , 11111>
IPv4,SGT: <10.11.11.4 , 11111>
IPv4,SGT: <10.11.11.5 , 11111>
IPv4,SGT: <10.11.11.6 , 11111>
IPv4,SGT: <172.168.1.1 , 65000>
IPv4,SGT: <172.168.1.2 , 65000>
IPv4,SGT: <172.168.1.3 , 65000>
IPv4,SGT: <172.168.1.4 , 65000>
IPv4,SGT: <172.168.1.5 , 65000>
IPv4,SGT: <172.168.1.6 , 65000>
IPv4,SGT: <172.168.1.7 , 65000>
IPv4,SGT: <172.168.1.8 , 65000>
IPv4,SGT: <172.168.1.9 , 65000>
IPv4,SGT: <172.168.1.10 , 65000>
IPv4,SGT: <172.168.1.11 , 65000>
IPv4,SGT: <172.168.1.12 , 65000>
IPv4,SGT: <172.168.1.13 , 65000>
IPv4,SGT: <172.168.1.14 , 65000>

Verify the expansion count on Device 1:

Device1# show cts sxp sgt-map

IP-SGT Mappings expanded:22
There are no IP-SGT Mappings

Save the configurations on Device 1 and Device 2 and exit global configuration mode.

Device1(config)# copy running-config startup-config
Device1(config)# exit

Device2(config)# copy running-config startup-config
Device2(config)# exit

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Feature Information for Cisco TrustSec Subnet to SGT Mapping

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Table 1 Feature Information for Cisco TrustSec Subnet to SGT Mapping

Feature Name

Releases

Feature Information

Cisco TrustSec Subnet to SGT Mapping

Cisco IOS XE Release 3.12S

Subnet to security group tag (SGT) mapping binds an SGT to all host addresses of a specified subnet. Once this mapping is implemented, Cisco TrustSec imposes the SGT on any incoming packet that has a source IP address which belongs to the specified subnet.

The following command was introduced: cts sxp mapping network-map.

In Cisco IOS XE Release 3.12S, support was added for the Cisco ASR 1000 Series Routers.