CCIE R&S Advanced Technologies Class v4.5 - BGP Conditional Route Injection

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	The fourth way that we have an option to originate prefixes in the BGP
0:00:18	is with the feature known as BGP conditioanl route injection.
0:00:22	Now, this is much less of a common design as compared to using just a network statement
0:00:28	or using the aggregate address command.
0:00:30	Where this is generally for the purpose of traffic engineering.
0:00:33	We are taking an aggregate
0:00:36	and from the aggregate, we are genertaing subnets.
0:00:40	So, it's the opposite of the aggregate address command,
0:00:43	where would aggregation we're taking the subnets
0:00:45	and then generating a less specific match from it.
0:00:48	With conditional route injection, we're taking a less specific match
0:00:51	and then generating subnets from it.
0:00:55	Now, the reason that we would want to do this
0:00:58	is that we have a shorter match to a particular destination,
0:01:03	then we want a particular peer
0:01:05	to send traffic for just a subset of that aggregate.
0:01:11	So, let's say here in AS 100,
0:01:14	we have four or three subnets that we're aggregating.
0:01:18	We have 150.28.1.0/24
0:01:23	150.28.4.0
0:01:27	150.28.6.0
0:01:31	All three of these prefixes, they're being aggregated together as 150.28.0.0/20
0:01:40	Router 1 is advertising this to 6.
0:01:42	It's advertising it to 4.
0:01:45	4 and 6 respectively are gonna be advertising this to AS 54.
0:01:50	If we look at the result of this and go to BB1 or BB3,
0:01:57	On BB1, let's look at the Show...
0:02:04	Show IP BGP.
0:02:08	Right now, we have the...
0:02:12	/20 aggregate.
0:02:13	Plus we have the more specific routes.
0:02:19	So, the first thing I'm gonna do is change this...
0:02:23	aggregation.
0:02:25	So that AS 54 is only receiving...
0:02:28	the /20.
0:02:30	They're not gonna be receiving the individual subnets.
0:02:35	So, to do this on router 6,
0:02:39	I'm going to filter inbound
0:02:42	as the prefixes are coming from switch 1.
0:02:48	I'm not going to accept the subnets in that direction.
0:02:52	Then likewise, on router 4, I'm not gonna accept these from router 5.
0:02:56	So, the only possible way that I can reach the subnets is gonna be in from router 1.
0:03:04	So, first, let's go to router 6.
0:03:10	And to ... Actually, to simplify this, let's look at the Show IP BGP Summary.
0:03:14	One thing I could do real quick
0:03:16	is going to the BGP process.
0:03:19	Then simply say, "For this neighbor, 155.28.67.7,"
0:03:24	"I wanna shut them down."
0:03:25	So, this is used to administartively disable a particular peering.
0:03:32	Which is different than simply removing the config.
0:03:36	Because now, whatever policy that I have applied on to the neighbor,
0:03:39	it's gonna stay in the running config.
0:03:41	When I want to reactivate them, the only thing I need to do is say,
0:03:44	"No neighbor shutdown."
0:03:47	So, now, I'll do the same thing on router 4.
0:03:51	If we Show IP BGP Summary,
0:03:54	I'll say under BGP 100, for the neighbor 155.28.0.5,
0:04:01	I want to shut them down.
0:04:07	Now, if we look at the Show IP BGP,
0:04:10	on either router 4 or router 6,
0:04:13	we should see just the /20.
0:04:17	So, router 1 is originating the aggregate.
0:04:20	It's going to both of its internal peers, router 4 and 6.
0:04:24	4 and 6 are then sending it to the external peers who are BB1 and BB3.
0:04:33	BB1 says, "I have two possible ways to get there."
0:04:36	One of them is directly from router 6.
0:04:39	One of them is indirectly through BB3.
0:04:43	If we look at the details of the prefix, we'll say Show IP BGP 150.28.0.0/20,
0:04:52	the vast majority of the attributes are the same here.
0:04:57	However, one of the routes is learned from an external peer.
0:05:01	One of them is coming from an internal peer.
0:05:04	So, BGP is part of the path selction, it will choose an EBGP route
0:05:09	over an iBGP route.
0:05:13	Assuming that the weight, the local preference and the AS path information is the same.
0:05:20	Now, this is separate from the administrative distance
0:05:23	because this decision happens in the BGP state machine.
0:05:27	Not one is getting installed into the routing table.
0:05:31	So, in the routing table, we still would prefer external BGP over internal BGP.
0:05:35	Because we have a distance of 20 for external versus 200 for internal.
0:05:41	But as part of the path selection,
0:05:43	we're gonna choose the external routes over the internal routes.
0:05:47	So, this then means from BB1's perspective, if we were to trace,
0:05:51	let's say router 1's loopback.
0:05:54	Trace 150.28.1.1
0:05:57	This is gonna go to the EBGP peer.
0:06:01	If I were to go to BB3,
0:06:04	and do the same thing, trace 150.28.1.1,
0:06:09	from their perspective, they're going to their EBGP peer, which is router 4.
0:06:16	So, this means that the inbound traffic from BB1 is going that way.
0:06:21	The inbound traffic rom BB3 is going that way.
0:06:26	Both of the routes that they're using
0:06:28	are the same longest match. BB1 is learning the /20,
0:06:33	as is BB3.
0:06:37	If I now wanted to change the path selection,
0:06:41	my options are limited because if I change the /20 on one exit point,
0:06:46	it's going to affect traffic for all of the individual subnets.
0:06:50	It's going to affect router 1, 4 and 6.
0:06:53	But then also any of the other destination. Router 3, router 2, router 5, etc.
0:07:01	So, now, with the BGP conditional route injection,
0:07:05	I could tell one of the exit points,
0:07:07	either router 4 or router 6,
0:07:09	that in addition to the aggregate,
0:07:12	I want to advertise selectively one of the individual subnets.
0:07:18	So, now, on router 6,
0:07:20	I'll say that when I'm sending the advertisement out to BB1,
0:07:24	not only will I send
0:07:27	the 150.28.0.0/20
0:07:32	but I also wanna advertise 150.28.1.0/24
0:07:44	Now, the key to this feature similar to the aggregation,
0:07:48	where aggregation says that the subnet needs to be in the BGP table before we can generate the summary.
0:07:54	Conditional route injection says that the summary needs to be in the BGP table
0:07:59	before we can generate the subnet.
0:08:04	Implementation wise, there's two different route maps that we're gonna for this.
0:08:08	The inject map is going to specify what's the actual route we wanna advertise.
0:08:14	So, in this case, that's gonna be router 1's loopback.
0:08:17	The exist map is going to match the aggregate.
0:08:20	And the neighbor that it is being learned from.
0:08:24	On router 6, this means that we're gonna match the /20.
0:08:28	And we're also gonna match router 1's address.
0:08:31	because that's where the prefix is being learned from.
0:08:36	This is similar to in IGP when we were changing the administrative distance on a per neighbor basis.
0:08:43	When we look at the routing table,
0:08:45	and on router 6, say, Show IP Route 150.28.0.0,
0:08:53	and look at the specific match for...
0:08:58	the 255.255.240.0
0:09:03	The routing table says that the route source is 150.28.1.1
0:09:14	So, when we look at the routing table, whatever value shows up after the from,
0:09:19	that's the source of the update.
0:09:23	So, in the exist map,
0:09:25	I need to match 150.28.0.0/20
0:09:29	and 150.28.1.1/32
0:09:36	So, on router 6, I actually need three separate prefix list.
0:09:40	One of them is gonn be for...
0:09:43	router 1's route source, which is 150.28.1.1/32
0:09:51	Another one that is for the aggregate.
0:09:57	The aggregate is 150.28.0.0/20
0:10:03	Then the third one is gonna be the subnet
0:10:07	that we're trying to generate.
0:10:09	In this case, I want to generate 150.28.1.0/24
0:10:17	Now, I could generate whatever I wanted to.
0:10:19	I could generate a /25 or some longer match
0:10:22	as long as it is encompass by the /20,
0:10:28	that's what our prerequisite is.
0:10:30	So, I can't generate 1.2.3.4/32
0:10:34	because that's not part of the summary, 150.28.0.0/20
0:10:41	So, I'm gonna advertise the /24
0:10:45	Next step is that I need two separate route-maps.
0:10:48	One of them is gonna match the route source and the aggregate.
0:10:51	That's the exist map.
0:10:54	Then the route-map that is matching the subnet is the inject map.
0:10:57	So, that's actually what I want to advertise.
0:11:02	First one is gonna match the aggregate
0:11:05	and the source.
0:11:08	This says, Match IP Address Prefix List
0:11:13	The Aggregate.
0:11:16	Then Match the IP Route Source.
0:11:19	This likewise is a prefix list that is router 1's route source.
0:11:26	Then I have the route-map that is to generate the subnet.
0:11:34	That is going to set IP address prefix list.
0:11:39	So, up to this point, we've only been doing matching with the route-maps for BGP.
0:11:45	In this case, we are actually setting the prefix because we are originating it.
0:11:56	So, the prefix list we are setting is the subnet.
0:11:59	That's gonna be what we are injecting.
0:12:01	Then under the BGP process, we'll say BGP Inject Map.
0:12:06	We're injecting what's matched in generate subnet.
0:12:12	But only if the aggregate is in the BGP table.
0:12:16	So, that is match the aggregate and the source.
0:12:22	On router 6, if we look at the Debug IP BGP,
0:12:26	we should see that the BGP process is now gonna look for the aggregate.
0:12:31	And if it finds it, it's then going to generate the...
0:12:36	/24
0:12:40	So, let's try sending a triggered update,
0:12:42	we'll say Clear IP BGP.
0:12:44	Star (*) Out.
0:12:58	And what I should have said here was Debug IP BGP Update, not Debug IP BGP.
0:13:04	So, let's try this again. Clear IP BGP Star (*) Out.
0:13:28	So, now, let's look at the...
0:13:31	Let's just look at the Show IP BGP.
0:13:33	If this worked, we should the /24 is now on the tabe.
0:13:38	But it says the originator is actually still router 1.
0:13:42	So, somewhere in this debug output, it should have said that we're actually doing the origination.
0:13:51	And we may not see it because I did the wrong debug before.
0:13:58	before the process started.
0:14:00	So, if we now look at the Show IP BGP 150.28.1.0/24,
0:14:09	it says that this was generated by
0:14:13	conditional route injection.
0:14:14	It was injected based on that particular path, the /24.
0:14:21	It says, this is coming from an aggregate
0:14:25	that was really originated by router 1.
0:14:27	The BGP prefix right now has RIB failure,
0:14:33	which means that it's not actually getting installed in the routing table.
0:14:36	So, this is considered an inactive prefix in the BGP table.
0:14:42	What RIB failure essentially means is that when we look at the Show IP Route,
0:14:46	and match that particular prefix,
0:14:50	there something else in the table
0:14:53	as opposed to the BGP route.
0:14:56	Now, specifically in this case, the reason why that BGP route is not installed,
0:15:02	is that we have an iBGP learned route with a distance of 200
0:15:07	versus the OSPF route with a distance of 110.
0:15:12	Although remember what we talked about the update rules
0:15:15	and the advertisement rules that are differnt in RIP and EIGRP
0:15:20	versus OSPF and BGP.
0:15:23	In BGP, as long as the prefix is a best route,
0:15:27	we can advertise it to the neighbors.
0:15:29	We don't necessarily need to install in the routing table
0:15:32	as long as it's installed in the BGP table.
0:15:37	So, now, if I were to go to BB1,
0:15:43	and look at the Show IP BGP,
0:15:47	we should see that now we have the /20 aggregate
0:15:52	but also the /24 subnet.
0:15:56	So, if we were now to do a trace route to router 1's loopback,
0:16:00	either from BB1 or BB3,
0:16:05	we should see that the traffic is always gonna go to router 6.
0:16:11	So, from BB3, we'll trace 150.28.1.1.
0:16:18	This link here, this is the connection
0:16:20	between BB1 and BB3.
0:16:24	Now, on the remote end, those neighbors don't actually have a route back to this.
0:16:28	So, what I need to do is source the packets
0:16:33	from something they do have a route to.
0:16:37	On BB3, if I look at the Show IP Route Connected,
0:16:42	this would be, let's say loopback 1.
0:16:54	From BB3, we'll say trace
0:16:58	to get to 150.28.1.1 from 28.119.17.1,
0:17:11	So, simply based on the fact that the longer match is only being advertised to BB1,
0:17:17	it now means that any traffic that is going to router 1's loopback
0:17:22	needs to take the link to BB1 first then to router 6 then down to router 1.
0:17:31	But just like the previous aggregation, the keypoint is that the network is still resilient
0:17:37	becasue if the link between router 6 and BB1 goes down,
0:17:40	we still have the route to the /20 via the other entry path.
0:17:50	There's a question here,
0:17:51	"Is it preferable to use an access list instead of a prefix list,
0:17:55	given that you can use the Show Acces List and see the hits against the list?"
0:18:00	The problem that you could run into when using an access list in BGP
0:18:04	is that if you use a standard access list,
0:18:07	you can only match on the address field and not on the subnet mask.
0:18:13	So, if theoretically, we had two prefixes that were different lengths but share the same address,
0:18:20	we would not be able to distinguish between them by using just a standard access list.
0:18:26	Now, we'll see later when we talk abuot some additional filtering techniques.
0:18:29	There is a way that you could use an extended access list in BGP
0:18:33	that will work basically the same way as a prefix list.
0:18:37	Where this was essentially a temporary workaround
0:18:40	that they came up with before they actually implemented the prefix list.
0:18:45	So, ideally, you would use the prefix list any time you're trying to match a route.
0:18:49	Because if we look at the final result of this on router 6,
0:18:54	say Show Run Include Route Map or...
0:18:59	Match or Set or Prefix...
0:19:06	or Inject.
0:19:11	Under the BGP process, we're saying, "Inject whatever Route is in the route map, generate subnet."
0:19:17	"But only if what's matched in the route-map, match aggregate and source..."
0:19:22	"is true."
0:19:26	So, match aggregate and source is saying, "If the prefix aggregate is in the BGP table
0:19:30	and it's being learned from this neighbor,
0:19:33	then we're allowed to generate the subnet.
0:19:37	So, the problem again with the access list is that if we were to match
0:19:41	150.28.0.0 in a standard ACL,
0:19:45	it wouldn't be able to tell the difference between the /20 and the /24 or a /16.
0:19:54	You'll also see that certain applications simply won't work
0:19:57	if you use and access list versus a prefix list.
0:20:01	And I believe this is one of them, when you're matching the route source.
0:20:06	I'm pretty sure you have to use the prefix list that has the /32.
0:20:10	You could try it out with the ACL and see if it works.
0:20:13	But design wise, there's really no reason why you would not use the prefix list.
0:20:18	The only case where you wouldn't is if the exam question says, "Don't use a prefix list."
0:20:23	But again, we'll see some work around later with that
0:20:26	using the extended access list in place of the prefix list.
0:20:37	So, documentation wise for this,
0:20:41	if we go under the...
0:20:45	configuration guide,
0:20:48	and I wanna say this is under...
0:20:53	configuring the basic BGP network..
0:20:56	So, again, you don't need to memorize where these different
0:20:59	configurations are located.
0:21:01	Just open up the differrent sections of the configuration guide
0:21:04	and use the find in page function of the browser.
0:21:08	So, you won't be able to search the documentation through the actual search engine,
0:21:13	but you can do a search on the individual webpage.
0:21:17	So, if I do control F and say Inject,
0:21:20	it's configuring a basic BGP network conditional route injection.

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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 Conditional Route Injection

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