The following illustration provides an overview of Next hop forwarding feature.

You can configure Next hop IP address at the SMF under DNN profile or IPAM profile. During PDU Establishment, the SMF relays the IPv4/IPv6 address over the N4 interface in the NEXT HOP IP private IE in a PFCP Session Establishment Request.

You can also configure the Next hop IP address at the UPF through Charging-Action.

Note	When Next hop address is provided by both SMF and UPF Charging-Action, the UPF Charging-Action Nexthop address takes precedence.

Configuration Priority

Configuration Use Cases

Interface

The following Private IEs are introduced in Sx/N4 Session Establishment message.

The following is a sample output of SX_SESSION_ESTABLISHMENT_REQUEST in which the SMF relays the Next hop IP to the UPF.

CREATE FAR:
  Type: 3
  Value:
   FAR ID:
     Type: 108
     Value: 0x80000002
   APPLY ACTION:
     Type: 44  
     Value:
       DROP: 0
       FORW: 1 
       BUFF: 0
       NOCP: 0
       DUPL: 0
   FORWARDING PARAMETERS:
     Type: 4
     Value:
       DESTINATION INTERFACE:
         Type: 42
         Value: CORE (1)
       PDN INSTANCE:
          Type: 22
          Value: intershat
          INNER PACKET MARKING:
            Type: 220
            TOS/TRAFFIC CLASS: 0xB8 0xFC
    NextHop ID:
      Value: 0x0001 

CREATE TRAFFIC ENDPOINT: 
    Type: 127  Length: 20
    Value:               
    Traffic Endpoint ID: 
        Type: 131  Length: 1
        Value: 0x0004       
        Hex: 0083 0001 04   
        Local F-TEID:       
            Type: 21  Length: 1
            Value:             
                CH: 1          
                IPv4: 0        
                IPv6: 0        
                CHID: 0        
            Hex: 0015 0001 04  
        Bearer Info:           
            Type: 225  Length: 6
            QCI: 5              
            ARP: 84             
            Charging ID: 5592407
            Hex: 00E1 0006 0554 0055 5557 
    Hex: 007F 0014 0083 0001 0400 1500 0104 00E1 
                 0006 0554 0055 5557                     
 NEXT HOP IP: 
    Type: 237  Length: 14
    Value:               
    NextHop ID:          
        Type: 238  Length: 1
        Value: 0x0001       
        Hex: 00EE 0001 01   
    IP ADDR:                
        Type: 239  Length: 5
        Value:              
            IPv4: 1                 
            IPv6: 0
            IPv4: 209.165.202.150
            IPv6:            
            Hex: 00EF 0005 020F 0F0F 0F
    Hex: 00ED 000E 00EE 0001 0100 EF00 0502 0F0F 
         0F0F
 

The following are the known limitations of this feature:

• Configuring next hop forwarding through AAA is not supported.

• Next hop address sent on RADIUS and Diameter (Redirect information from PCF) interfaces is not qualified.

• When you configure next hop forwarding in DNN profile and IPAM, the next hop is only seen in Sx Establishment, and not in Create FAR IE of Sx Session Modification Request.

At the UPF, use the following CLI commands to configure Next hop forwarding through Charging Action.

configure 
   active-charging service service_name  
      charging-action charging_action_name 
         nexthop-forwarding-address ipv4_address/ipv6_address 

NOTES:

• charging-action charging_action_name: Specifies the name of a charging action. charging_action_name must be an alphanumeric string of 1–63 characters and can contain punctuation characters. Each charging action must have a unique name.

• nexthop-forwarding-address ipv4_address/ipv6_address: Configures the next hop forwarding address.

At the SMF, use the following CLI commands to configure Next hop forwarding through the DNN profile.

configure 
   profile dnn intershat  
         nexthop-forwarding-address { ipv4 ipv4_address| ipv6  ipv6_address } 
         end 

NOTES:

• nexthop-forwarding-address { ipv4 ipv4_address | ipv6 ipv6_address } : Configures the Next hop forwarding address.

  • ipv4_address : Configures IPv4 address.

  • ipv6_address : Configures IPv6 address (supports colon-separated hexadecimal notation).

At the SMF, use the following CLI command to configure Next hop forwarding at the IP pool through the IPAM profile for IPv4 addresses.

configure 
   ipam
      instance instance_id 
         address-pool pool_name 
            ipv4 
            address-ranges 
               address-range start_ipv4_address end_ipv4_address nexthop-forwarding-address nexthop_forwarding_address 
               prefix-range prefix_value length  prefix_length nexthop-forwarding-address nexthop_forwarding_address 
               split-size per-cache number_of_addresses 
               split-size per-dp number_of_addresses 
               commit 

NOTES:

• address-pool pool_name : Specify the name of the address pool. pool_name must be a string.

• ipv4 : Enter the IPv4 mode of the pool.

• address-ranges : Specify the starting address of the IPv4 address range. Enter the IPv4 address range and prefix range addresses with the next hop forwarding address.

  • address-range start_ipv4_address end_ipv4_address nexthop-forwarding-address nexthop_forwarding_address : Specify the starting and the ending addresses of the IPv4 address range with the next hop forwarding address.

  • prefix-range prefix_value length prefix_length : Specify the prefix value and the length within the IPv4 address.

  • nexthop-forwarding-address nexthop_forwarding_address : Specify the next hop forwarding address.

• split-size per-cache number_of_addresses : Specify the number of IPv4 addresses per chunk for IPAM cache allocation. Specify in the power of 2. The IPAM server consumes this configuration. number_of_addresses must be an integer in the range of 2-262144.

• split-size-per-dp number_of_addresses : Specify the number of IPv4 addresses per chunk for data plane allocation. Specify in the power of 2. The IPAM cache consumes this configuration.

  number_of_addresses must be an integer in the range of 2-262144.

To configure the IPv6 address with the next hop configuration for IPv6 pools and address ranges, use the following sample configuration:

configure 
   ipam
      instance instance_id 
         address-pool pool_name 
            ipv6 
            address-ranges 
               address-range start_ipv6_address end_ipv6_address nexthop-forwarding-address nexthop_forwarding_address 
               prefix-range prefix_value length prefix_length nexthop-forwarding-address nexthop_forwarding_address 
                 split-size per-cache number_of_addresses 
                 split-size per-dp number_of_addresses 
                 exit  
                 prefix-range prefix_value length prefix_length nexthop-forwarding-address nexthop_forwarding_address 
               commit 

NOTES:

• address-pool pool_name : Specify the name of the address pool. pool_name must be a string.

• ipv6 : Enter the IPv6 mode of the pool.

• address-ranges : Specify the IPv6 address ranges and prefix range addresses with the next hop forwarding address.

  Note	IANA IPv6 configuration is used by BNG.

  • address-range start_ipv6_address end_ipv6_address : Specify the starting and the ending addresses of the IPv6 address range.

  • nexthop-forwarding-address nexthop_forwarding_address : Specify the next hop forwarding address.

  • prefix-range prefix_value length prefix_length : Specify the prefix value and length within the IPv6 address.

  • nexthop-forwarding-address nexthop_forwarding_address : Specify the next hop forwarding address.

• prefix-ranges : Specify the prefix ranges of an IPv6 address.

  Note	SMF supports only IAPD IPv6 configuration.

  • split-size per-cache number_of_addresses : Specify the number of IPv6 addresses per chunk for IPAM cache allocation.

  • split-size-per-dp number_of_addresses : Specify the number of IPv6 addresses per chunk for the data plane allocation.

  • prefix-range prefix_value length prefix_length nexthop-forwarding-address nexthop_forwardng_address : Specify the prefix value and the length within the IPv6 address with the next hop forwarding address.

UPF supports segmenting the enterprise traffic using Virtual LAN (VLAN). VLANs enable a single physical LAN segment to be further segmented into smaller virtual networks so that the groups of ports are isolated from one another, as if they were on physically different segments. In VLAN segmentation, the UEs belonging to different classes are assigned to different VLANs for traffic isolation.

VLAN Segmentation can be achieved using two methods:

1. Next Hop Forwarding

2. Virtual Routing and Forwarding

In the VLAN segmentation using next hop forwarding, the IP pool is mapped with the VLAN tags. This mapping takes place at the SMF. The IP pool is associated with the next hop forwarding address on the N6 interface, which is reachable through the VLAN associated with the IP pool as configured on the Control Center.

Note	This feature is supported on both 1-Rack Unit and 3-Rack Unit architectures and can support up to 16 VLANs on the N6 interface.

Achieving VLAN segmentation using next hop forwarding follows the given process:

• The SMF sends a N4 Session Establishment Request with the next hop forwarding address to the UPF.

• The UPF associates the next hop forwarding address with the session. This association allows the session management layer on the UPF to program the VPP to perform next hop forwarding of the uplink packets belonging to that session.

• The session manager on the UPF creates the uplink streams in the VPP Fastpath conduit with next hop forwarding operation with appropriate next hop IP. Therefore, the UPF does not look at the actual IP destination route to forward the packets. Rather, it relates the UE’s IP address with the next hop IP and forwards the uplink packet on the VLAN from where the next hop IP is reachable.

To configure VLAN segmentation on UPF using next hop forwarding, use the following configuration:

config
   port ethernet slot/port
      no shutdown
      vlan vlan_tag_ID
      no shutdown
      bind interface interface_name context_name
      end
      context context_name
         { ip | ipv6 } address address subnetmask [ secondary ] 
         end 

NOTES:

• port ethernet slot/port —Ethernet port or slot that will contain the VLAN tag.

• no shutdown —It enables or disables the traffic over a specified VLAN.

• vlan vlan_tag_ID —Enters the VLAN configuration mode.

• no shutdown —Enables or disables traffic over the current VLAN.

• bind interface interface_name context_name —It binds a virtual interface and context to support VLAN service.

• context context_name —Configures the context to in which the interface is created.

• { ip | ipv6 } address address subnetmask [ secondary ] —Maps the IP pools with the configured VLANs. The [ secondary ] keyword assigns multiple IP addresses to the interface.

In order to forward the packets to the next hop IP, it requires the UPF to perform source-based routing and also learn the MAC address of the next hop IP by sending an ARP request to the next hop.

Configuring network reachability allows the UPF to test the network device by sending the ping packets to the destination.

To test and detect network reachability or failure on UPF for IPv4 addresses, use following configuration:

config 
   context context_name 
   nw-reachability server server_name  [ remote-addr  ip_addr  ]  [ local-addr ip_addr  ]  

NOTES:

• nw-reachability server server_name [ remote-addr ip_addr ] [ local-addr ip_addr ] —This CLI adds or deletes a reachability-detect server. The [ local-addr ip_addr specifies the source IP from which the packets are sent and the [ remote-addr ip_addr specifies the destination IP to send the ping packets for detecting network failure or reachability.

To test and detect network reachability or failure on UPF for IPv6 addresses, use the following configuration:

config 
   context context_name 
      ip access-list  acl_name 
      { deny | permit } [ log ] any 
      exit 
   nw-reachability server server_name  [ remote-addr  ip_addr  ]  [ local-addr ip_addr  ]  
   end if_name 
   interface if_name 
      ipv6 address ipv6_address ipv6_mask 
         bfd interval interval_value min_rx rx_value multiplier multiplier_value 
         exit 
      port ethernet slot/port 
         no shutdown 
         vlan vlan_tag_ID 
         no shutdown 
         bind interface interface_name context_name 
         end 

NOTES:

• ip access-list acl_name : ip access-list specifies the type of subscriber traffic and the direction (uplink, downlink, or both) traffic is redirected. The ip access-list must be specified in the context in which the subscriber authentication is performed.

• { deny | permit } [ log ] any : Indicates the rule, when matched, drops or allows the corresponding packets. [ log ] indicates that all the packets which match the filter are to be logged.

  any indicates that all the packets will match the filter regardless of the source and/or the destination.

• interface if_name : Specifies the interface in which the to enable BFD.

• ipv6 address ipv6_address ipv6_mask : Specifies the IPv6 address for configuring the static routes.

• bfd interval interval_value min_rx rx_value multiplier multiplier_value : bfd interval interval_value specifies the transmit interval of control packets in milliseconds as an integer from 50 through 10000. min_rx rx_value specifies the minimum receive interval for control packets in milliseconds as an integer from 50 through 10000. multiplier multiplier_value specifies the value used to compute hold-down time as an integer from 3 through 50.

This section describes the operations, administration, and maintenance support for this feature.

This section provides information about show commands and their outputs in support of this feature.

show subscriber user-plane-only full all

The output of this show command is enhanced to include the following fields introduced in support of this feature.

• Next Hop Ip Address - Displays the configured Nexthop IP address.

Note	Next Hop Ip Address field is displayed only if the Nexthop IP address is relayed from the SMF. This field is not displayed if Nexthop IP address is configured only at the UPF using Charging-Action.