1 00:00:08,860 --> 00:00:20,110 In this topology, if PC 1 sends a broadcast where will it go? So what will happen if we put this PC into 2 00:00:20,110 --> 00:00:27,180 a separate VLAN will broadcast be forwarded out of this port and this port? 3 00:00:27,300 --> 00:00:30,610 Switch 1 has no configuration at the moment. 4 00:00:30,620 --> 00:00:38,880 So show MAC address table we can see that a source MAC address was learnt on gigabit 01 and 5 00:00:38,880 --> 00:00:41,450 this MAC address was learnt on gigabit 00. 6 00:00:41,460 --> 00:00:48,630 In other words the switch to back to the router as well as the ostinato device sending synthetic or 7 00:00:49,020 --> 00:00:58,950 generated frames. Show VLAN brief at the moment we only have the default VLANs gigabit 01 belongs 8 00:00:58,950 --> 00:01:00,490 to VLAN 1. 9 00:01:00,720 --> 00:01:10,380 So I'll create VLAN 2 and then go on to gigabit 01 and type switch port access VLAN 2 to put 10 00:01:10,530 --> 00:01:16,260 that port into VLAN 2, so show interface gigabit 01 switch port 11 00:01:16,260 --> 00:01:19,550 this port is now in the VLAN 2. 12 00:01:19,580 --> 00:01:23,870 We have moved the PC into a separate VLAN. 13 00:01:23,970 --> 00:01:28,560 So what I'll do is stop Ostinato and then start it again. 14 00:01:28,560 --> 00:01:30,700 So we're still generating frames 15 00:01:30,960 --> 00:01:34,170 these are broadcast frames that are being generated. 16 00:01:34,380 --> 00:01:41,810 Do we see any traffic on that interface? No broadcasts are being received on this interface. 17 00:01:43,070 --> 00:01:47,310 What about this interface? 18 00:01:47,420 --> 00:01:54,510 Again no broadcasts from the PC are being received even though the PC is sending the broadcasts 19 00:01:57,290 --> 00:02:04,430 because the switch has been configured with VLANs broadcasts received on this interface are not forwarded 20 00:02:04,790 --> 00:02:10,840 out of gigabit 02 or 00 because they are in separate VLANs. 21 00:02:11,150 --> 00:02:19,330 But if we configured gigabit 00 as a trunk so we use the command switch port trunk encapsulation dot 22 00:02:19,340 --> 00:02:22,770 1q switch port mode trunk. 23 00:02:22,820 --> 00:02:27,830 What would happen now? Would broadcast be forwarded on that port? 24 00:02:28,040 --> 00:02:38,370 So show interface gigabit 00 switch port it's configured for trunking. 25 00:02:38,760 --> 00:02:40,790 It's operating as a trunk. 26 00:02:40,800 --> 00:02:44,560 We can see that by typing show interface trunk. 27 00:02:44,970 --> 00:02:53,990 So gigabit 00 has been manually configured as a trunk, will broadcast before it across that port? 28 00:02:54,000 --> 00:03:04,380 So this is the Wireshark capture on gigabit 00 from the switch to gigabit 00 on the router 29 00:03:04,500 --> 00:03:13,140 and as you can see broadcast frames are being sent they are being put in to VALN 2. 30 00:03:13,180 --> 00:03:22,120 In other words they are tagged with 82 dot1q tag 2 because the traffic was sent on a port 31 00:03:22,150 --> 00:03:23,740 in VLAN 2. 32 00:03:23,740 --> 00:03:27,440 So this port is an access port in VLAN 2 and this is a trunk port. 33 00:03:27,620 --> 00:03:34,640 So on the trunk port they are tagged with VLAN 2 but broadcasts are being forwarded to the router. 34 00:03:35,020 --> 00:03:38,990 The router however will not forward those broadcasts on. 35 00:03:39,010 --> 00:03:45,560 So even if we configured the router as a router on the stick it would still not forward the frames. 36 00:03:45,580 --> 00:03:54,490 So at the moment gigabit 00 is configured with an IP address but even if we did the following and 37 00:03:54,490 --> 00:04:00,010 type encapsulation dot1q and specify VLAN 2 38 00:04:03,490 --> 00:04:11,720 broadcast would not be received by the router but the router would not forward them on even if we configured 39 00:04:13,940 --> 00:04:23,170 an IP address of let's say 10 120 254 on that interface because routers don't forward broadcasts 40 00:04:23,180 --> 00:04:24,870 by default. 41 00:04:24,950 --> 00:04:33,900 So I've got this IP address configured on gigabit 00.2 but if we do a capture on this interface 42 00:04:36,910 --> 00:04:44,110 what you'll notice is no broadcasts are being forwarded on because routers block broadcasts by default. 43 00:04:44,830 --> 00:04:50,170 I hope you found this video very useful, if it's been of benefit to you please like it and please subscribe 44 00:04:50,170 --> 00:04:51,450 to my YouTube channel. 45 00:04:51,700 --> 00:04:54,060 I wish you all the very best.