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    How to Trace Data Packets from Gn to Gi Interfaces

    Requirements

    This example uses the following hardware and software components:

    • An operational MX chassis
    • Junos OS Mobility package

    Tracing Data Packets

    This section shows how to trace Gn to Gi (GTP-U) data packets.

    Configuration

    Setting up Data Packet Tracing

    Step-by-Step Procedure

    The following procedure shows how to trace GTP-U (Gn to Gi) data packets.

    1. Verify that the Gn/S5 interface is receiving packets.
      user@host> show jnh if statistics
              IFL Name               Index               In(Packets/Bytes)            Out(Packets/Bytes)
      ...
           
    2. Verify that the filter is seeing GTP-U packets by finding the index of the implicit RTT filter used by mobility applications.
      user@host> show filter UE address prefix
      Program Filters:
      ---------------
         Index     Dir     Cnt    Text     Bss  Name
      --------  ------  ------  ------  ------  --------
      
      Term Filters:
      ------------
         Index    Semantic   Name
      --------  ---------- ------
             2  Classic    __default_bpdu_filter__
         17000  Classic    __default_arp_policer__
         57008  Classic    __cfm_filter_shared_lc__
         65280  Classic    __auto_policer_template__
         65281  Classic    __auto_policer_template_1__
         65282  Classic    __auto_policer_template_2__
         65283  Classic    __auto_policer_template_3__
         65284  Classic    __auto_policer_template_4__
         65285  Classic    __auto_policer_template_5__
         65286  Classic    __auto_policer_template_6__
         65287  Classic    __auto_policer_template_7__
         65288  Classic    __auto_policer_template_8__
      46137345  Classic    HOSTBOUND_IPv4_FILTER
      46137346  Classic    HOSTBOUND_IPv6_FILTER
      46137347  Classic    __me_uplink_exception_filter_ipv4__
      46137349  Classic    __me_uplink_exception_filter_ipv6__
      67108864  Classic    __mobile_gw_impl_filter__           <----
    3. Verify that the filter has the correct GGSN IP address (172.23.9.100 in the following output) in the filter.
      user@host> show filter index 67108864 program
      Filter index = 67108864
      Optimization flag: 0xf7
      Filter notify host id = 0
      Filter properties: None
      Filter state = CONSISTENT
      term IP-Fragments
      term priority 0
          is-fragment
              value & 0x3fff != 0x0000
              false branch to match protocol in rule GTP-U
          destination-address
              172.23.9.100/32 <----
              false branch to match protocol in rule GTP-U
      
          then
              action next-hop, type (nh-id)
                      4194308
              count __mgw_ip_frags_count
      term GTP-U
      term priority 0
          protocol
               17
              false branch to match action in rule default-term
          port
               2152
              false branch to match port in rule GTP-C
          destination-address
              172.23.9.100/32 <----
              false branch to match port in rule GTP-C
      
          then
              action next-hop, type (nh-id)
                      4194308
              count __gtpu_pkt_count
      term GTP-C--
      term priority 0
          port
               2123
              false branch to match port in rule sp-1/0_LIBAAA_udp_start_10000
          destination-address
              172.23.9.100/32
              false branch to match port in rule sp-1/0_LIBAAA_udp_start_10000
      
          then
              action next-hop, type (nh-id)
                      4194307
              count __gtpc_pkt_count
    4. Verify that the implicit RTT firewall filter counter for GTP-U is incrementing.
      user@host> show filter index 67108864 counters
      Filter Counters/Policers:
         Index               Packets                 Bytes  Name
      --------  --------------------  --------------------  --------
      67108864                     2                   452  __gtpc_pkt_count
      67108864                     2                   584  __gtpu_pkt_count <----
      67108864                     0                     0  __mgw_ip_frags_count
      67108864                     0                     0  __sp-1-0_GTP_pkt_count
      67108864                     0                     0  __sp-1-0_LIBAAA_pkt_count
      67108864                     0                     0  __sp-1-0_LIBCHRG_pkt_count
    5. Verify that the GTP-U ingress ucode NH is created and is not marked as Discard.
      user@host> show mobile-edge halp ucode-nhs
      Nexthop ID                         Purpose
      ------------------------------------------------
      
      4194306                            GTPv0 parsing ucode
      4194307                            GTP-C v1/v2 parsing ucode
      4194308                            GTP-U ingress ucode
      4194309                            DHCP parsing ucode
      4194310                            GTP-C table NH
      4194311                            GTP-U table NH
      4194312                            GTP-U restore packet context ucode
      4194313                            IP frag load balancing ucode
      
      
      host@user> show nhdb id 4194308 extensive
      ID    Type    Interface   Next Hop Addr    Protocol     Encap     MTU     Flags  PFE internal Flags
      4194308   Unicast  -              -                     GTP-U             -     0  0x00000000 0x00008004
      
      Flags:              0x00000000
      PFE internal flags: 0x00008004
      
      Dram Bytes     : 268
      PreComputed MTU: 0
      Flags          : 0x0
      Parent NHID    :0
      
      
      PFE:0
      
      Encap-ptr chain:
      ----------------
      
      Dram Bytes: 268
    6. Verify that the GTP-U route table is set up correctly on the Gn ingress Packet Forwarding Engine.
      host@user> show route gtp-u
      default                                            Service   653
      0.0.0.0                                            Service   647
      0.32/16                                           Unicast   666 mif.16000

      Note: Data TEID route should be present in the gtp-u table (0.32/16 in this case, which is teid starting with 0x02). Since any Packet Forwarding Engine can be ingress Packet Forwarding Engine, the same GTP-U route table is present on all Packet Forwarding Engines. NH-id 666 in the route corresponds to the anchor Packet Forwarding Engine.

    7. To find the anchor Packet Forwarding Engine, execute the following command. The L2 interface identifies the anchor Packet Forwarding Engine. In the output below, fpc 0 pic 0 is the anchor Packet Forwarding Engine.
      host@user> show nhdb id 666 extensive
       ID    Type    Interface    Next Hop Addr    Protocol     Encap     MTU     Flags  PFE internal Flags
        666   Unicast  mif.16000      default                IPv4   Unspecified     0  0x10000000 0x00000000
      
      Flags:              0x10000000
      PFE internal flags: 0x00000000
        L2-Interface: pfe-0/0/0.16383 (81) <------- ANCHOR PFE
      
      Dram Bytes     : 268
      PreComputed MTU: 0
      Flags          : 0x10000000
      Parent NHID    :0
              Feature List: NH
                 [pfe-0]: 0xce811db000200005;
                f_mask:0x00400000; c_mask:0x80000000; f_num:11; c_num:1,  inst:0
              Idx#9      ucast:
                 [pfe-0]: 0xce811db000200005
      
      <........SNIP................>
    8. Verify that the subscriber is installed in the anchor Packet Forwarding Engine (LU id = 0 here).
      host@user> show vbf hw 0 subscriber-table uplink
      +----------+----------+--------+--------+--------+-------+--------+----------+----------+
      | RINDEX   | TEID     | VRF ID | TFT ID | CONFIG | FLAGS | CHRGID | CHRGADDR | IPADDR   |
      +----------+----------+--------+--------+--------+-------+--------+----------+----------+
      |0xf       |0x200001  |0x0     |0x0     |0x2210  |0x1    |0x0     |0x80000e  |0x27270802|
      |0xb       |0x200000  |0x0     |0x0     |0x2210  |0x1    |0x0     |0x800000  |0x27270801|
      +----------+----------+--------+--------+--------+-------+--------+----------+----------+
      | TOTAL: 2                                                                              |
      +----------+----------+--------+--------+--------+-------+--------+----------+----------+
    9. Verify that there are no GTP parsing errors on the anchor Packet Forwarding Engine.

      Note: Also verify that the In stats on the Gn (S5) interface are incrementing.

      st@user> show vjnh 0 exceptions terse

    Published: 2011-11-16