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Multicast Reflector - performance/quality issue



I have configured a multicast reflector on C7604. It translates destination multicast->multicast.

Unfortunatelly the quality of translated video traffic is poor. The same traffic goes through router at the same incomming ant outgoing interface, but only original movie goes correctly.

On the top of the windows you can see multicast destinations addresses. It differs in 3rd octet - this is what translation does.

The router's configuration is following: (only related parts)


ip multicast-routing


vlan 10


interface GigabitEthernet2/2
 description multicast source interface
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 10
 switchport mode trunk


interface GigabitEthernet2/2
 description multicast receiver interface
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 10
 switchport mode trunk



interface Vlan10
 description multicast source L3 interface
 ip address
 ip pim sparse-mode


interface Vif1
 description multicast reflector interface
 ip address
 ip pim sparse-mode
 ip service reflect Vlan10 destination to mask-len 32 source
 ip igmp static-group



There is totally no cpu load, this router stays out of any additional traffic. So what cause the problem?

Interesting is, that corrupted frames are noticed on receiver software, but outgoing interface is clear:


#sh int gi1/3
GigabitEthernet1/3 is up, line protocol is up (connected)
  Hardware is C7600 1Gb 802.3, address is 30e4.db33.3cc0 (bia 30e4.db33.3cc0)
  Internet address is
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s
  input flow-control is off, output flow-control is on
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:03, output 00:00:12, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 1214000 bits/sec, 161 packets/sec
  5 minute output rate 2655000 bits/sec, 310 packets/sec
  L2 Switched: ucast: 81470 pkt, 5506930 bytes - mcast: 654403 pkt, 46087950 bytes
  L3 in Switched: ucast: 6507385 pkt, 5574437081 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 4652244 pkt, 1783930222 bytes mcast: 6859161 pkt, 9342177282 bytes
     7282403 packets input, 5630637613 bytes, 0 no buffer
     Received 690711 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     9060192 packets output, 7716061155 bytes, 0 underruns
     0 output errors, 0 collisions, 2 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out







Problem solved.

Traffic need to be marked with DF bit.

Pls show me how

It have to be done at the source. I couldn't achive it on 7600.