CCIE R&S Advanced Technologies Class v4.5

Transcript

1	Introduction	0h 43m
2	Using the Cisco Documentation	0h 52m
3	Ethernet Overview, Layer 2 Switchports, Trunking, ISL, 802.1q, DTP	0h 47m
4	VTP, VTP Authentication, VTP Pruning	1h 02m
5	VTP Prune Eligible List, VTP Transparent, VTP Troubleshooting, Trunk Allowed List, Extended VLANs	0h 48m
6	VLAN and VTP Review	0h 19m
7	SVIs, Native Routed Interfaces, Router-on-a-Stick	0h 46m
8	Layer 2 EtherChannel, EtherChannel Load Balancing, Layer 3 EtherChannel	0h 57m
9	802.1q Tunneling, Layer 2 Protocol Tunneling, EtherChannel over 802.1q Tunneling	1h 03m
10	STP Root Bridge Election, STP Root Port Election, STP Designated Port Election, STP Priority, STP Cost, STP Port-Priority	1h 46m
11	STP Review	0h 12m
12	STP Timers, STP PortFast	0h 34m
13	STP UplinkFast	0h 11m
14	STP BackboneFast	0h 12m
15	STP BPDU Filter	0h 13m
16	STP BPDU Guard	0h 11m
17	STP Root Guard	0h 11m
18	STP Loop Guard, Unidirectional Link Detection (UDLD)	0h 11m
19	Multiple Spanning-Tree Protocol (MST)	0h 40m
20	Rapid Spanning-Tree Protocol (RSTP), Rapid-PVST	0h 18m
21	MST with Multiple Regions	0h 33m
22	Flex Links	0h 16m
23	Frame Relay	0h 39m
24	Frame Relay Configuration Part 1	0h 34m
25	Frame Relay Configuration Part 2	0h 41m
26	Frame Relay Switching	0h 27m
27	Back-to-Back Frame Relay	0h 08m
28	Frame-Relay End-to-End Keepalives	0h 18m
29	PPP, PPP PAP Authentication, PPP CHAP Authentication	0h 59m
30	PPPoFR, PPPoE	0h 40m
31	Transparent Bridging, IRB	0h 32m
32	Fallback Bridging	0h 14m
33	IP Routing Overview, Switching Paths, Static Routing	0h 42m
34	Static Routing Examples	0h 25m
35	IP Default-Gateway, IP Default-Network	0h 14m
36	On-Demand Routing (ODR)	0h 07m
37	Floating Static Routes	0h 10m
38	Backup Interface	0h 29m
39	Enhanced Object Tracking, IP SLA, Reliable Static Routing	0h 21m
40	Policy Routing	0h 43m
41	GRE Tunneling, GRE Recursive Routing Errors	0h 27m
42	Reliable Backup Interface with GRE	0h 25m
43	RIP Overview, RIP Versions, RIP Auto-Summary	0h 48m
44	RIP Split-Horizon, RIP Timers	0h 22m
45	RIP Broadcast Updates, IP Directed Broadcast, IP Broadcast-Address, Smurf Attacks, Fraggle Attacks	0h 16m
46	RIP Unicast Updates	0h 03m
47	RIP Offset-List	0h 18m
48	RIP Authentication	0h 11m
49	RIP Summarization	0h 10m
50	Prefix-Lists, RIP Distribute-List Filtering, RIP Administrative Distance Filtering	0h 48m
51	RIP Default Routing, RIP Conditional Default Routing	0h 18m
52	RIP Triggered, RIP Validate Update Source,	0h 12m
53	EIGRP Overview	0h 29m
54	EIGRP Auto-Summary	0h 07m
55	EIGRP Split-Horizon	0h 11m
56	EIGRP Update Types, EIGRP Neighbor, EIGRP Passive-Interface	0h 24m
57	EIGRP Hello-Interval, EIGRP Hold-Time	0h 05m
58	EIGRP Authentication	0h 11m
59	EIGRP Time Based Authentication	0h 25m
60	EIGRP Path Selection, EIGRP Metric Weights, EIGRP Traffic Engineering	0h 47m
61	EIGRP Unequal Cost Load Balancing, EIGRP Variance	0h 19m
62	EIGRP QUERY, EIGRP Summarization, EIGRP Leak-Map	0h 28m
63	EIGRP Stub Router Advertisement	0h 22m
64	EIGRP Default Routing	0h 13m
65	EIGRP Route Filtering	0h 11m
66	EIGRP Router-ID	0h 07m
67	Miscellaneous EIGRP Features	0h 02m
68	OSPF Overview	0h 27m
69	Establishing OSPF Adjacencies, Understanding the OSPF Database	0h 43m
70	OSPF Network Type Broadcast, OSPF DR/BDR Election, OSPF over NBMA, OSPF Network Type Non-Broadcast and Point-to-Multipoint	0h 56m
71	OSPF Network Type Point-to-Point, OSPF Network Type Mismatch	0h 13m
72	OSPF Network Type Point-to-Multipoint Non-Broadcast, OSPF Per Neighbor Cost	0h 17m
73	OSPF Network Type Loopback	0h 02m
74	OSPF Path Selection	0h 27m
75	OSPF Convergence Timers	0h 09m
76	OSPF Authentication	0h 12m
77	OSPF Summarization	0h 32m
78	OSPF Stub Areas, OSPF Totally Stubby Areas, OSPF NSSAs, OSPF Totally NSSAs	0h 40m
79	Controlling OSPF NSSA Redistribution	0h 02m
80	OSPF Type 7 to 5 Translator Election, OSPF LSA Type 3 Filter, OSPF Forwarding Address Suppression	0h 24m
81	Route Redistribution Overview	0h 36m
82	Route Redistribution Configuration & Verification, Connected Redistribution	0h 22m
83	OSPF External Path Selection, TCL PING Scripting	0h 33m
84	Routing Loops Overview, EIGRP Route Loop Prevention	0h 55m
85	Metric Based Routing Loops, Route Tagging	0h 46m
86	Administrative Distance Based Routing Loops, Debug IP Routing, IP Route Profile	0h 58m
87	BGP Overview, BGP Peering Types	0h 51m
88	Establishing BGP Peerings, EBGP Multihop, BGP Neighbor Disable Connected Check, BGP TTL Security	0h 49m
89	BGP 4-Byte ASNs	0h 20m
90	BGP Local AS, BGP Peer Groups	0h 30m
91	BGP Next-Hop Self, BGP Next-Hop Processing	0h 30m
92	BGP Route Reflectors	0h 37m
93	Large Scale BGP Route Reflectors with Clusters	0h 34m
94	BGP Confederation	0h 37m
95	BGP NLRI Advertisements, BGP Network Statement, BGP Redistribution	0h 43m
96	BGP Aggregation, BGP Aggregation & Summary-Only, BGP Aggregation & Unsuppress-Map	0h 46m
97	BGP Origin, BGP Aggregation & AS-Set, BGP Aggregation & Advertise-Map	0h 22m
98	BGP Conditional Route Injection	0h 21m
99	BGP Bestpath Selection, BGP Multipath, BGP Weight	0h 53m
100	BGP Local Preference, BGP Local Preference and Communities, BGP AS-Path Prepending,	0h 30m
101	BGP MED, BGP MED Missing As Worst, BGP Deterministic MED	0h 17m
102	BGP Communites, BGP Regular Expressions	0h 43m
103	BGP Filtering, BGP Convergence Timers, BGP Default Routing, Miscellaneous BGP Features	0h 24m
104	MPLS Overview, MPLS Label Distribution Protocol (LDP)	1h 05m
105	MPLS Tunnels, MPLS Penultimate Hop Popping (PHP)	0h 40m
106	MPLS Layer 3 VPNs Overview, VRF Lite	0h 36m
107	MPLS Layer 3 VPNs and VPNv4 BGP	1h 08m
108	MPLS Layer 3 VPN Verification & Troubleshooting	0h 49m
109	MPLS Layer 3 VPN OSPF PE-CE Routing Overview	0h 06m
110	MPLS Layer 3 VPN OSPF PE-CE Routing Path Selection & Sham-Links	2h 01m
111	MPLS Layer 3 VPN OSPF PE-CE Routing Loop Prevention & Down-Bit, OSPF Capability VRF-Lite	0h 40m
112	IPv6 Overview, IPv6 ICMPv6 ND, IPv6 over NBMA	0h 44m
113	IPv6 Routing Overview, IPv6 Static Routing	0h 28m
114	IPv6 RIPng	0h 20m
115	IPv6 EIGRPv6	0h 09m
116	IPv6 OSPFv3	0h 31m
117	MP-BGP for IPv6	0h 26m
118	IPv6 Tunneling	1h 13m
119	Multicast Overview, IGMP	0h 34m
120	PIM Overview	0h 18m
121	PIM Dense Mode	1h 03m
122	PIM Sparse Mode	0h 30m
123	PIM Sparse Mode Configuration	0h 36m
124	PIM Sparse Mode RPF & RP Troubleshooting	0h 27m
125	Auto-RP, Multicast over GRE Tunnels	0h 53m
126	Bootstrap Router (BSR), Bidirectional PIM, Source Specific Multicast (SSM)	0h 40m
127	MSDP, Anycast RP	0h 27m
128	IPv6 Multicast Routing	0h 24m
129	QoS Overview, IntServ QoS, DiffServ QoS, IP Precedence, DSCP, MQC, HQF	0h 41m
130	MQC Classification	0h 44m
131	FIFO, FQ, WFQ, CBWFQ, HQF	0h 50m
132	LLQ	0h 23m
133	WRED	0h 31m
134	Traffic Shaping, Traffic Policing	0h 40m
135	Frame Relay Traffic Shaping (FRTS)	0h 33m
136	RSVP	0h 07m
137	Catalyst 3560 QoS	1h 00m
138	IOS Security Overview, Access Lists (ACLs)	0h 58m
139	Time Based ACLs, Dynamic ACLs	0h 33m
140	Reflexive ACLs	0h 21m
141	TCP Intercept, Content Based Access Control (CBAC)	0h 34m
142	Zone Based Policy Firewall (ZBPF)	1h 09m
143	AAA, Local Authentication, Local Authorization, Role Based CLI Access	0h 43m
144	Port Security, Static CAM Entries, Storm Control, 802.1X Authentication, PACLs, RACLs, VLAN Access Maps (VACLs)	0h 48m
145	DHCP Snooping, Dynamic ARP Inspection (DAI), IP Source Guard	0h 12m
146	Protected Ports, Private VLANs	0h 25m
147	IP Services Overview, HSRP	1h 10m
148	VRRP, GLBP	0h 28m
149	NAT	0h 42m
150	DHCP, DNS	0h 30m
151	NetFlow	0h 09m
152	WCCP, Miscellaneous IP Services	0h 06m
153	System Management Overview, NTP, NTP Authentication	0h 24m
154	SNMP, RMON	0h 38m
155	Syslog, Telnet, SSH, Banners	0h 21m
156	EEM Scripting, Miscellaneous System Management	0h 26m
Total Duration		81h 42m

Slides - Diagrams

Slides - Introduction

Slides - Ethernet Switching

Slides - Advanced Ethernet Switching

Slides - Frame Relay

Slides - PPP

Slides - Transport Bridging

Slides - Redistribution

Slides - IOS Security

Slides - Layer 2 Security

Slides - IP Services

Slides - System Management

0:00:13	In our next section here, we're gonna look at how the new 4 byte BGP autonomous system number is used.
0:00:19	And how this can affect the legacy old BGP implementations that do not support the 4 byte AS.
0:00:26	And the different encodings that we can use in order to transit the 4 byte autonomous sytem through
0:00:32	the networks that do not support that type of value.
0:00:36	So, again, as I mentioned, the new notation for the 4 byte AS number is sometimes called the AS .notation
0:00:43	where we have two 2 byte values that are separated by a dot in the middle.
0:00:48	Technically, you could also disrepresent this as a full decimal number.
0:00:53	But a lot of the times it's easier to read it as the AS .notation
0:00:58	similar to how the BGP community values work.
0:01:02	So, technically, the community is just a binary number that's inside the BGP update.
0:01:07	But when we look at visually in the configuration,
0:01:10	a lot of times, it makes more sense to look at it with the colon notation in the middle
0:01:14	as opposed to just a full decimal value.
0:01:16	So, we'll look at that in communities a little bit later.
0:01:20	But here first, we're gonna look at the 4 byte autonomous system number.
0:01:24	Now, the devices that will support it in our topology are the ones that are running the later versions of 12.4 T.
0:01:31	Which specifically, they are routers 4, 5 and 6 here.
0:01:36	So, the other devices, the catalyst switches and some of the older IOS versions of the router,
0:01:41	these are only gonna support the 2 byte versions.
0:01:46	So, we're going to configure a couple of different peerings here.
0:01:49	Where on routers 4, 5, and 6,
0:01:51	instead of using AS numbers 4, 5, and 6 as we did in the previous example,
0:01:56	on router 6, I'm gooing to use 1.6
0:01:59	On router 4, 1.4
0:02:04	And on router 5, 1.5
0:02:08	So, these will still be EBGP peerings.
0:02:12	We'll say, on switch 1, we'll have AS 7.
0:02:14	On switch 2, we'll have AS 8.
0:02:17	On switch 4, we'll have AS 10.
0:02:20	So, once we establish the peerings, then we'll do some basic advertisements between the neighbors.
0:02:25	And look at what is the end result here for the BGP AS path
0:02:28	inside the 4 byte autonomous systems and the 2 byte autonomous sytems.
0:02:38	So, to start, let's go to...
0:02:41	Swith 4 and switch 2 here.
0:02:45	And we have a directly connected link between them that is 155.28, 108.8 on switch 2.
0:02:52	And 108.10 on switch 4.
0:02:55	So, we'll configure BGP AS 10.
0:02:58	I'm gonna peer with the address of switch 2.
0:03:03	And there in this particular AS, which is gonna be AS number 8.
0:03:08	Now, additionally, I'm going to advertise some of my connected links in the BGP.
0:03:14	We'll say network 155.28.10.0, with the mask of /24.
0:03:21	This is my connected VLAN interface.
0:03:25	So, once the peering is up between these two neighbors,
0:03:27	I should be able to look at the Show IP BGP output
0:03:30	and then see that switch 4 is advertising that particular prefix.
0:03:39	Next, between routers 4, 5, and 6,
0:03:42	I'm going to remove the previous configuration.
0:03:50	And it should be a 10 there, not an 8.
0:03:53	Remove the previous configuration, we'll say on router 5, No router BGP 5.
0:03:58	And we'll replace this by router BGP 1.5
0:04:03	So, there's really nothing too special about this configuration from the routers that do support it.
0:04:08	I'll say that, i'll configure the peering with router 4, who is an AS 1.4
0:04:15	I'm also gonna be peering with switch 2,
0:04:19	who is in the 2 byte AS 8,
0:04:23	which could also be denoted as 0.8
0:04:28	So, in the AS path information, sometimes, you'll see this as 0.8
0:04:32	Configuration wise, most of the versions are still gonna take this as the decimal value.
0:04:37	But it's the same value when we're looking at it a bit wise. If its' 0.8 or just decimal 8.
0:04:45	On router 4, we'll do the same thing.
0:04:48	So, no router BGP 4. We're going to replace this by router BGP 1.4
0:04:54	Then we'll have the peering with router 5,
0:04:58	who is an AS 1.5.
0:05:01	And also, I'll have a peering with router 6,
0:05:05	who is an AS...
0:05:09	1.6
0:05:15	Then on router 6, no router BGP 6.
0:05:20	Router BGP 1.6
0:05:25	I'm peering with router 4.
0:05:30	Remote AS 1.4. And then on router 5 or router 6, we're also going to originate a prefix.
0:05:37	So, let's say any of these connected networks, let's say the loopback, 150.128.6.0...
0:05:45	/24,
0:05:49	we're going to originate this into the network.
0:05:53	So, from router 6, if we look at the Show IP BGP,
0:05:56	we should see that our local loopback has then been advertised into the BGP table.
0:06:01	This then means we're gonna advertise it to our EBGP peer who is router 4.
0:06:06	From router 4, if we look at the same output, the Show IP BGP,
0:06:11	we should shortly see the loopback interface coming in from router 6.
0:06:16	And we should see the AS path is going to include the 4 byte AS which is 1.6
0:06:22	as opposed to the previous just 6.
0:06:27	Now, you'll see a lot of the times when you're doing these BGP configurations,
0:06:31	that the protocol is fairly slow to converge,
0:06:34	So, you may need to move on to another configuration for 5 or 10 minutes and then come back
0:06:38	and see if everything has synchronized.
0:06:45	So, we see we have the prefix 150.28.6.0,
0:06:48	it says theat the autonomous system path is now AS 1.6.
0:06:53	So, it's simply a different notation in the AS path information.
0:06:58	If we were to go to router 5,
0:07:00	as we would expect, this prefix is gonna have the AS path that starts with 1.4,
0:07:06	who is the AS we're learning it from.
0:07:09	And then it's beeing originated in AS 1.6.
0:07:16	Next, we're gonna configure a peering
0:07:19	between router 5 and switch 2.
0:07:23	The issue here is that switch 2's BGP process
0:07:28	doesn't understand the 4 byte autonomous system that router 5 has configured.
0:07:32	So, from router 5's perspective, there's no problem.
0:07:35	It's just gonna say neighbor, switch 2's address and then remote AS 8.
0:07:40	But on switch 2, there's no option syntax wise for us to say, Neighbor 155.28.58.5, remote AS...
0:07:53	remote AS 1.5 Because this version doesn't support it.
0:07:57	So, we need to figure out what is the actual value
0:08:00	that router 5 is using here in the backwards compatilbility.
0:08:06	Now, we can see once I configured
0:08:08	the neighbor statement from switch 2 over to router 5.
0:08:13	There's a BGP notification message received that says the peers in the wrong AS.
0:08:19	There's a 2 byte value that is 5BA0, which is a hex of a decimal value.
0:08:27	That's telling us what is the actual autonomous sytem number that we are receiving from them.
0:08:34	So, if we were to take this value in hex, which is 5BA0,
0:08:42	convert this to decimal, it's that reserved AS number 23456.
0:08:48	So, form the perspective of any device that only supports the 2 byte system number,
0:08:55	essentially, the local AS that 5 is sending to switch 2 is 23456.
0:09:04	We'll also see that any 4-byte autonomous system that is in our AS path,
0:09:10	is then gonna be encoded as AS number 23456.
0:09:14	So, ultimately, once we go to switch 4 and look at the final AS path,
0:09:20	let's say that it's something that is originated by router 6,
0:09:24	it would say, "It originated in 23456."
0:09:29	It pass through 23456, which is really 1.4 and 1.6 respectively.
0:09:37	Then it pass through 23456 again, which is really router 5.
0:09:42	And then it pass through AS 8 and then it was learned by us.
0:09:48	So, if we were to go now to switch 2,
0:09:53	and changed this neighbor peering,
0:09:57	so that the neighbor statement goes to 23456,
0:10:05	we should see that the session is gonna come up.
0:10:08	Now, also, we'll also do the same thing between switch 1 and router 6.
0:10:13	So, router 6 is gonna say that I have a peering that goes over to switch 1.
0:10:19	They're in AS 7.
0:10:22	Since switch 1 doesn't support the 4-byte AS number,
0:10:26	we need to say that this neighbor who is router 6,
0:10:31	is in AS 23456.
0:10:35	Additionally, I'm going to generate a local advertisement.
0:10:38	Okay, I have a connected link here 155.28.7.0
0:10:47	We look at the Show IP BGP.
0:10:51	We see that we are learning the local route that we are originating, which is the 7.0
0:10:57	We're learning the route from router 6 to 6.0
0:11:00	and then the one that's coming all the way from the other end of the network, which is switch 4.
0:11:05	So, in the AS path information here,
0:11:09	we're showing all of them as 23456
0:11:12	where really there's an encoding as an optional transitive attribute on the update
0:11:19	that tells us, this isn't really 23456.
0:11:22	What this is 1.6, 1.4 and 1.5
0:11:32	So, if switch 1 were to have some other peering beyond it,
0:11:38	that was going to some router that did support the 4-byte autonomous systems,
0:11:43	we would see that the full AS path is going to be maintained.
0:11:48	But the keypoint here is that from the device that only supports the 2-byte AS,
0:11:53	they need to say that the remote autonomous system is 23456.
0:12:00	Beyond that, there's no other configuration that we need to do in order to support this.
0:12:05	So, if we were to look at this from switch 4's perspective,
0:12:09	and Show IP BGP,
0:12:15	we see all of the real autonomous system paths have been replaced by 23456.
0:12:20	Now, where this is gonna make more sense,
0:12:22	let's say that the peerings, I'm gonna change the peering design a little bit here so that
0:12:29	1.6 is gonna peer with switch 4.
0:12:36	And then switch 4 is gonna peer back with router 4.
0:12:41	So, there's someone that has just a 2 byte autonomous system,
0:12:45	that's gonna be in the transit path between these 4 byte AS numbers.
0:12:52	So, to simplify this a little bit, we'll put the configuration in no path,
0:12:56	where from router 6, this is BGP 1.6
0:13:00	I need a neighbor peering that goes to 155.28.10.10, who is an AS 10.
0:13:11	Since this is a multihop peering, I need to say EBGP multihop.
0:13:16	And also my update source is loopback 0.
0:13:22	Then router 4 is essentially gonna do the same thing.
0:13:27	But it's coming from 1.4
0:13:38	Then on switch 4, I'll get rid of its previous peerings. We'll restart this with peerings that goes to...
0:13:41	150.28.6.6,
0:13:45	who I think is in 23456.
0:13:49	Then the same with router 4.
0:13:57	They're both EBGP multihop peerings and I'm gonna need to...
0:14:03	originate both of them from my loopback 0.
0:14:07	So, you could see by doing the configurations in no path,
0:14:11	it's a little bit easier to see the overall design of what's going on.
0:14:14	And to make sure that we just don't leave out one key command that's gonna cause the peerings not to work.
0:14:20	So, we'll configure this on router 4.
0:14:32	And under BGP 1.4,
0:14:35	I'm gonna remove the previous peering that was to router 6.
0:14:41	So, now, we have the peering that's going to...
0:14:48	the peering that's going to switch 4.
0:14:55	Router 6 likewise.
0:15:00	And then...
0:15:02	switch 4.
0:15:04	Now, one thing that you do need to be aware of here,
0:15:08	that if you are doing EBGP multihop peerings between
0:15:12	the loopbacks or any of the non-connected interface,
0:15:15	we need to avaoid what could be considered BGP race condition.
0:15:21	In the case that the neighbor's address that we're using is also a route that we're learning from BGP.
0:15:32	So, if we look at the cionfiguration of switch 4 here,
0:15:37	switch 4 says, "I'm peering with the loopback interface of router 6."
0:15:41	So, in order to establish this peering, we're assuming that there's some sort of IGP route to get there.
0:15:47	So, if we Show IP Route for 150.28.6.6,
0:15:52	I should have an IGP route to get there.
0:15:55	But now, in this particular design, router 6 is also advertising that prefix into BGP.
0:16:02	So, we end up in a kind of a recursivce loop in the routing table.
0:16:07	Where it says to get to 150.28.6.6,
0:16:12	use 150.28.6.6.
0:16:16	So, eventually, we'll see that the BGP peering is gonna time out here.
0:16:20	Because BGP cannot rely on itself for transport.
0:16:24	And this is what's known as the BGP race condition.
0:16:27	The same type of logic we talked about before in GRE tunnels.
0:16:32	Where if the GRE tunnel destination is routed out to tunnel itself,
0:16:38	you end up in that recursive error in the routing table,
0:16:40	which is essentially what's happening here.
0:16:43	So, what I would need to do on router 6,
0:16:46	basically, I don't want to advertise that loopback into BGP.
0:16:56	Because this is already advetised into IGP.
0:17:02	And that's what I'm using to terminate this sessions on.
0:17:07	So, i'll advertise something that's connected. Let's say 155.28.67.0/24.
0:17:23	So, now, the peerings are passing from 6 to switch 4,
0:17:29	from switch 4 to router 4.
0:17:32	Then from router 4 to 5.
0:17:34	From 5 to switch 2,
0:17:38	which is an 8.
0:17:39	I'm originating the prefix here.
0:17:43	So, if we look at...
0:17:46	router 6,
0:17:49	and Show IP BGP,
0:17:52	we should see that on switch 4, Show IP BGP,
0:18:03	we will advertise network 155.28.10.0
0:18:08	/24.
0:18:14	So, switch 4 is now locally originating that.
0:18:17	When it gets to router 6, router 6 should say it's coming from AS 10.
0:18:22	Which is what we would expect because this is the normal 2 byte AS of the neighbor.
0:18:29	6 is now passing this to...
0:18:35	Actually, 6 is passing it to no one.
0:18:36	I need to look at this from...
0:18:44	from the other way, so I'm gonna go to switch 2 and advertise that link there.
0:18:52	Let's go to switch 2.
0:18:55	Router BGP 8, we'll say Network 155.28.8.0.
0:19:01	So, this is one of my connected LAN segments.
0:19:05	So, switch 2 is locally originating that.
0:19:09	It goes from switch 2 to router 5.
0:19:14	5 should see this as the normal 2 byte AS, which it does.
0:19:21	When this gets to router 4,
0:19:24	router 4 sees router 5's 4 byte AS.
0:19:28	Because both of these are supporting the 4 byte value.
0:19:32	Then from router 4, it's going to down to switch 4 who doesn't support it.
0:19:36	So, we'll see that this value should then be replaced by 23456.
0:19:42	Which it is here, it's being replaced twice by 23456.
0:19:46	One's for router 4's AS number, one's for 5's.
0:19:50	It was originated in AS 8.
0:19:51	But then finally, when it goes to router 6, we'll see that this information was maintained.
0:19:57	So, as a temporary place holder,
0:20:01	that new optional transit of attribute of the AS 4 path is maintaining.
0:20:10	Now, whether all vendors are going to support this optional transit of attribute,
0:20:14	it depends on there individual implementaion.
0:20:16	But IOS to IOS, there's no problem with it.
0:20:18	You may see that if you are going to other vendors called that's older,
0:20:23	they may not be able to support this.
0:20:25	But the idea is that we're essentially tunneling the autonomous system path
0:20:30	through the older devices that don't support this 4 byte values.

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CCIE R&S Advanced Technologies Class v4.5
Title:	CCIE R&S Advanced Technologies Class v4.5
Duration:	81h 42m
The CCIE Routing & Switching Advanced Technologies Class is the first step in understanding CCIE level technologies and is a companion to the Advanced Technologies Lab Workbook. Each technology you need to know for the CCIE Routing & Switching lab will be described in detail using an instructor led hands on demonstration. The class consists of over 80 hours of in depth explanations and examples.
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BGP 4-Byte ASNs

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