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Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 855

Example when recursive route lookups are enabled, In fact, this route is a directly-connected route.

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Enabling next-hop recursion 26 Example when recursive route lookups are enabled When recursive next-hop lookups are enabled, the device recursively looks up the next-hop gateways along the route until the device finds an IGP route to the BGP route's destination. Here is an example. BigIron RX# show ip bgp route Total number of BGP Routes: 5 Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED H:HISTORY I:IBGP L:LOCAL M:MULTIPATH S:SUPPRESSED Prefix Next Hop Metric LocPrf Weight Status 1 0.0.0.0/0 10.1.0.2 0 100 0 BI AS_PATH: 65001 4355 701 80 2 102.0.0.0/24 10.0.0.1 1 100 0 BI AS_PATH: 65001 4355 1 3 104.0.0.0/24 10.1.0.2 0 100 0 BI AS_PATH: 65001 4355 701 1 189 4 240.0.0.0/24 102.0.0.1 1 100 0 BI AS_PATH: 65001 4355 3356 7170 1455 5 250.0.0.0/24 209.157.24.1 1 100 0 I AS_PATH: 65001 4355 701 The first lookup results in an IBGP route, to network 102.0.0.0/24. BigIron RX# show ip route 102.0.0.1 Total number of IP routes: 38 Network Address Gateway 102.0.0.0 10.0.0.1 AS_PATH: 65001 4355 1 Port 1/1 Cost 1 Type B Since the route to 102.0.0.1/24 is not an IGP route, the device cannot reach the next hop through IP, and thus cannot use the BGP route. In this case, since recursive next-hop lookups are enabled, the device next performs a lookup for 102.0.0.1's next-hop gateway, 10.0.0.1. BigIron RX# show ip bgp route 102.0.0.0 Number of BGP Routes matching display condition : 1 Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED H:HISTORY I:IBGP L:LOCAL M:MULTIPATH S:SUPPRESSED Prefix Next Hop Metric LocPrf Weight Status 1 102.0.0.0/24 10.0.0.1 1 100 0 BI AS_PATH: 65001 4355 1 The next-hop IP address for 102.0.0.1 is not an IGP route, which means the BGP route's destination still cannot be reached through IP. The recursive next-hop lookup feature performs a lookup on 10.0.0.1's next-hop gateway: BigIron RX# show ip route 10.0.0.1 Total number of IP routes: 38 Network Address Gateway 10.0.0.0 0.0.0.0 AS_PATH: 65001 4355 1 Port 1/1 Cost Type 1 D This lookup results in an IGP route. In fact, this route is a directly-connected route. As a result, the BGP route's destination is now reachable through IGP, which means the BGP route is eligible for installation in the IP route table. Here is the BGP route in the IP route table. BigIron RX# show ip route 240.0.0.0/24 Total number of IP routes: 38 Network Address Gateway 240.0.0.0 10.0.0.1 AS_PATH: 65001 4355 1 Port 1/1 Cost Type 1 B BigIron RX Series Configuration Guide 783 53-1001810-01

Section	Page
BigIron RX	1
Contents	3
About This Document	41
In this chapter	41
Audience	41
Supported hardware and software	41
List of supported features	42
Unsupported features	44
What’s new in this document	45
Enhancements and configuration notes in release 02.7.02	45
Enhancements and configuration notes in release 02.7.01	46
Enhancements and configuration notes in release 02.7.00	46
Enhancements and configuration notes in release 02.6.00	48
Enhancements and configuration notes in patch release 02.5.00c	50
Enhancements and configuration notes in patch release 02.5.00b	51
Summary of enhancements and configuration notes in release 02.5.00	51
Summary of enhancements and configuration notes in patch release 02.4.00c	52
Summary of enhancements and configuration notes in release 02.4.00	53
Summary of enhancements in patch release 02.3.00a	57
Summary of enhancements and configuration notes in release 02.3.00	58
Summary of enhancements and configuration notes in 02.2.01	63
Summary of enhancements in release 02.2.00g	67
Summary of enhancements and configuration notes in 02.2.00	68
Document conventions	69
Text formatting	69
Command syntax conventions	69
Notes, cautions, and danger notices	69
Notice to the reader	70
Related publications	70
Getting technical help or reporting errors	70
Web access	71
E-mail access	71
Telephone access	71
Getting Started with the Command Line Interface	73
In this chapter	73
Logging on through the CLI	73
On-line help	74
Command completion	74
Scroll control	74
Line editing commands	75
EXEC commands	75
Global level	76
CONFIG commands	76
Accessing the CLI	79
Navigating among command levels	80
CLI command structure	80
Searching and filtering output	81
Allowable characters for LAG names	86
Syntax shortcuts	86
Saving configuration changes	86
Getting Familiar With the BigIron RX Series Switch Management Applications	89
In this chapter	89
How to manage BigIron RX Series switch	89
Logging on through the CLI	89
On-line help	90
Command completion	90
Scroll control	90
Line editing commands	91
Searching and filtering output from CLI commands	91
Allowable characters for LAG names	95
Logging on through the Web Management Interface	96
Web Management Interface	97
Logging on through IronView Network Manager	98
Using a Redundant Management Module	99
In this chapter	99
How management module redundancy works	99
Management module redundancy overview	99
Management module switchover	100
Switchover implications	101
Management module redundancy configuration	103
Changing the default active Chassis slot	103
Managing management module redundancy	103
File synchronization between the active and standby management modules	104
Manually switching over to the standby management module	106
Rebooting the active and standby management modules	106
Monitoring management module redundancy	107
Determining management module status	107
Displaying temperature information	108
Displaying switchover information	108
Flash memory and PCMCIA flash card file management commands	110
Management focus	111
Flash memory file system	111
PCMCIA flash card file system	112
Wildcards	113
Formatting a flash card	114
Determining the current management focus	114
Switching the management focus	115
Displaying a directory of the files	115
Displaying the contents of a file	117
Displaying the hexadecimal output of a file	118
Creating a subdirectory	118
Removing a subdirectory	120
Renaming a file	121
Changing the read-write attribute of a file	121
Deleting a file	122
Recovering (“undeleting”) a file	123
Appending a file to another file	124
Copying files using the copy command	124
Copying files using the cp command	129
Loading the software	129
Saving configuration changes	131
File management messages	132
Securing Access to Management Functions	133
In this chapter	133
Securing access methods	133
Restricting remote access to management functions	135
Using ACLs to restrict remote access	135
Restricting remote access to the device to specific IP addresses	138
Specifying the maximum number of login attempts for Telnet access	140
Restricting remote access to the device to specific VLAN IDs	140
Disabling specific access methods	141
Setting passwords	143
Setting a Telnet password	143
Setting passwords for management privilege levels	144
Recovering from a lost password	146
Displaying the SNMP community string	146
Disabling password encryption	146
Specifying a minimum password length	147
Setting up local user accounts	147
Configuring a local user account	148
Configuring SSL security for the Web Management Interface	150
Enabling the SSL server on the device	150
Importing digital certificates and RSA private key files	151
Generating an SSL certificate	151
Configuring TACACS/TACACS+ security	152
How TACACS+ differs from TACACS	152
TACACS/TACACS+ authentication, authorization, and accounting	152
TACACS/TACACS+ configuration considerations	156
Enabling SNMP to configure TACACS/TACACS	157
Identifying the TACACS/TACACS+ servers	157
Specifying different servers for individual AAA functions	158
Setting optional TACACS/TACACS+ parameters	158
Configuring authentication-method lists for TACACS/TACACS+	160
Configuring TACACS+ authorization	161
Configuring TACACS+ accounting	164
Configuring an interface as the source for all TACACS/TACACS+ packets	166
Displaying TACACS/TACACS+ statistics and configuration information	167
Configuring RADIUS security	168
RADIUS authentication, authorization, and accounting	168
RADIUS configuration considerations	171
RADIUS configuration procedure	171
Configuring Brocade-specific attributes on the RADIUS server	172
Enabling SNMP to configure RADIUS	173
Identifying the RADIUS server to the BigIron RX	173
Specifying different servers for individual AAA functions	174
Setting RADIUS parameters	174
Configuring authentication-method lists for RADIUS	175
Configuring RADIUS authorization	176
Configuring RADIUS accounting	178
Configuring an interface as the source for all RADIUS packets	179
Displaying RADIUS configuration information	180
Configuring authentication-method lists	181
Configuration considerations for authentication-method lists	182
Examples of authentication-method lists	183
Configuring Basic Parameters	185
In this chapter	185
Entering system administration information	186
Configuring Simple Network Management Protocol(SNMP) traps	186
Specifying an SNMP trap receiver	187
Specifying a Single trap source	187
Setting the SNMP Trap holddown time	188
Disabling SNMP traps	188
Disabling Syslog messages and traps for CLI access	189
Configuring an interface as the source for all Telnet packets	190
Cancelling an outbound Telnet session	191
Configuring an interface as the source for all TFTP packets	191
Configuring an interface as the source for Syslog packets	192
Specifying a Simple Network Time Protocol (SNTP) server	193
Setting the system clock	194
New Daylight Saving Time (DST)	196
Configuring CLI banners	196
Setting a message of the day banner	196
Setting a privileged EXEC CLI level banner	197
Displaying a message on the console when an incoming Telnet session is detected	197
Configuring terminal display	198
Checking the length of terminal displays	198
Enabling or disabling routing protocols	198
Displaying and modifying system parameter default settings	199
Enabling or disabling Layer 2 switching	201
CAM partitioning for the BigIron RX	202
Re-distributing CAM allocations	202
Nexthop table	203
Changing the MAC age time	204
Configuring static ARP entries	204
Configuring Interface Parameters	205
In this chapter	205
Assigning a port name	205
Assigning an IP address to a port	206
Speed/Duplex negotiation	206
Disabling or re-enabling a port	207
Changing the default Gigabit negotiation mode	208
Changing the negotiation mode	208
Disabling or re-enabling flow control	208
Specifying threshold values for flow control	209
Locking a port to restrict addresses	209
Wait for all cards feature	210
Port transition hold timer	210
Port flap dampening	210
Modifying port priority (QoS)	212
Assigning a mirror port and monitor ports	212
Configuration guidelines for monitoring traffic	213
Configuring port mirroring and monitoring	213
Monitoring an individual trunk port	214
Mirror ports for Policy-Based Routing (PBR) traffic	215
About hardware-based PBR	215
Configuring mirror ports for PBR traffic	215
Displaying mirror and monitor port configuration	216
Enabling WAN PHY mode support	216
Configuring IP	217
In this chapter	217
Overview of configuring IP	217
The IP packet flow	218
ARP cache table	219
Static ARP table	219
IP Route table	220
IP forwarding cache	221
Basic IP parameters and defaults	221
When parameter changes take effect	221
IP global parameters	222
IP interface parameters	224
Configuring IP parameters	225
Configuring IP addresses	226
Changing the network mask display to prefix format	228
Configuring the default gateway	229
GRE IP tunnel	229
IPv6 over IPv4 tunnels in hardware	234
Configuring Domain Name Server (DNS) resolver	238
Adding host names to the DNS cache table	239
Configuring packet parameters	243
Changing the encapsulation type	243
Setting maximum frame size per PPCR	244
Changing the MTU	245
Changing the router ID	246
Specifying a single source interface for Telnet, TACACS/TACACS+, or RADIUS packets	247
Configuring an interface as the source for Syslog packets	249
IP fragmentation protection	250
IP option attack protection	250
IP receive access list	250
Configuring ARP parameters	251
How ARP works	251
Rate limiting ARP packets	252
Applying a rate limit to ARP packets on an interface	253
Clearing the rate limit for ARP packets	254
Changing the ARP aging period	254
Creating a floating static ARP entry	256
Static route ARP validation check	257
Configuring forwarding parameters	258
Disabling ICMP messages	260
Disabling ICMP redirect messages	262
Configuring static routes	263
Static route tagging	268
Configuring a default network route	272
Configuring IP load sharing	273
Default route ECMP	276
IP receive access list	277
Configuring IRDP	278
Configuring UDP broadcast and IP helper parameters	280
Configuring BootP/DHCP forwarding parameters	283
Displaying IP information	285
Displaying IP interface information	287
Displaying interface name in Syslog	288
Displaying ARP entries	289
Displaying the forwarding cache	291
Displaying the IP route table	292
Clearing IP routes	295
Displaying IP traffic statistics	295
Displaying TCP traffic statistics	298
Link Aggregation	301
In this chapter	301
Link aggregation overview	301
LAG formation rules	302
LAG load sharing	304
Hash based load sharing	304
Migration from a pre-02.6.00 trunk or LACP configuration	305
Configuration of a LAG	306
Creating a Link Aggregation Group (LAG)	307
Deploying a LAG	309
Commands available under LAG once it is deployed	310
Configuring ACL-based mirroring	310
Disabling ports within a LAG	311
Enabling ports within a LAG	311
Monitoring an individual LAG port	311
Assigning a name to a port within a LAG	312
Enabling sFlow forwarding on a port within a LAG	312
Setting the sFlow sampling rate for a port within a LAG	312
Displaying LAG information	313
Displaying LAG statistics	317
Configuring LLDP	319
In this chapter	319
Terms used in this chapter	319
LLDP overview	320
Benefits of LLDP	320
General operating principles	321
Operating modes	321
LLDP packets	322
TLV support	322
MIB support	325
Syslog messages	325
Configuring LLDP	325
Configuration notes and considerations	326
Enabling and disabling LLDP	326
Changing a port’s LLDP operating mode	327
Specifying the maximum number of LLDP neighbors	328
Enabling LLDP SNMP notifications and Syslog messages	329
Specifying the minimum time between SNMP traps and Syslog messages	329
Changing the minimum time between LLDP transmissions	330
Changing the interval between regular LLDP transmissions	330
Changing the holdtime multiplier for transmit TTL	331
Changing the minimum time between port reinitializations	331
LLDP TLVs advertised by the Brocade device	332
Displaying LLDP statistics and configuration settings	338
LLDP configuration summary	338
LLDP statistics	339
LLDP neighbors	340
LLDP neighbors detail	341
LLDP configuration details	343
Resetting LLDP statistics	344
Configuring Uni-Directional Link Detection (UDLD)	345
In this chapter	345
Configuration considerations	346
Configuring UDLD	346
Changing the keepalive interval	346
Changing the keepalive retries	347
Displaying UDLD information	347
Displaying information for all ports	347
Displaying link-keepalive information	347
Displaying information for a single port	349
Clearing UDLD statistics	350
VLANs	351
In this chapter	351
Overview of Virtual Local Area Networks (VLANs)	351
Tagged, untagged, and dual-mode ports	351
Protocol-based VLANs	353
VLAN configuration rules	354
VLAN ID range	354
Tagged VLANs	354
VLAN hierarchy	354
Multiple VLAN membership rules	355
Layer 2 control protocols on VLANs	355
Configuring port-based VLANs	355
VLAN byte accounting	356
Strictly or explicitly tagging a port	358
Assigning or changing a VLAN priority	358
Assigning a different ID to the default VLAN	359
Configuring protocol-based VLANs	359
Configuring an MSTP instance	360
Configuring virtual routing interfaces	360
Bridging and routing the same protocol simultaneously on the same device	361
Integrated Switch Routing (ISR)	362
VLAN groups	363
Configuring a VLAN group	363
Configuring super aggregated VLANs	365
Configuring aggregated VLANs	367
Complete CLI examples	368
Configuring 802.1q-in-q tagging	371
Configuration rules	372
Enabling 802.1Q-in-Q tagging	372
Example configuration	374
Configuring 802.1q tag-type translation	374
Configuration rules	376
Enabling 802.1q tag-type translation	377
Private VLANs	378
Implementation notes	379
Configuration notes	379
Configuring a private VLAN	380
Enabling broadcast, multicast or unknown unicast traffic to the private VLAN	382
CLI example for Figure 30	383
Other VLAN features	383
Allocating memory for more VLANs or virtual routing interfaces	383
Hardware flooding for Layer 2 multicast and broadcast packets	383
Unknown unicast flooding on VLAN ports	384
Flow based MAC learning	385
Configuring uplink ports within a port-based VLAN	385
Configuring control protocols in VLANs	386
Other configuration options	386
Displaying VLAN information	386
Displaying VLAN information	386
Displaying VLAN information for specific ports	387
Displaying VLAN status and port types	388
Displaying VLAN group information	389
Transparent firewall mode	389
Enabling a transparent firewall	389
Configuring Spanning Tree Protocol	391
In this chapter	391
IEEE 802.1D Spanning Tree Protocol (STP)	391
Enabling or disabling STP	391
Default STP bridge and port parameters	393
Changing STP bridge parameters	394
Changing STP port parameters	394
STP root guard	394
Spanning Tree Protocol (STP) BPDU guard	396
Displaying STP information	396
IEEE Single Spanning Tree (SSTP)	402
SSTP defaults	402
Enabling SSTP	403
Displaying SSTP information	404
PVST/PVST+ compatibility	404
Overview of PVST and PVST+	405
VLAN tags and dual mode	405
Enabling PVST+ support	406
Displaying PVST+ support information	406
Configuration examples	407
SuperSpan™	409
Customer ID	410
BPDU forwarding	410
Configuring SuperSpan	415
Configuring Rapid Spanning Tree Protocol	419
In this chapter	419
Overview of Rapid Spanning Tree Protocol	419
Bridges and bridge port roles	419
Assignment of port roles	420
Ports on Switch 1	421
Ports on Switch 2	421
Ports on Switch 3	421
Ports Switch 4	422
Edge ports and edge port roles	422
Point-to-point ports	423
Bridge port states	423
Edge port and non-edge port states	424
Changes to port roles and states	424
State machines	424
Handshake mechanisms	425
Convergence in a simple topology	435
Convergence at start up	436
Convergence after a link failure	438
Convergence at link restoration	439
Convergence in a complex RSTP topology	441
Propagation of topology change	443
Compatibility of RSTP with 802.1D	446
Configuring RSTP parameters	447
Enabling or disabling RSTP in a port-based VLAN	447
Enabling or disabling RSTP on a single spanning tree	448
Disabling or enabling RSTP on a port	448
Changing RSTP bridge parameters	448
Changing port parameters	449
Fast port span	450
Fast uplink span	453
Displaying RSTP information	455
Metro Ring Protocol (MRP) Phase 1 and 2	459
In this chapter	459
Metro Ring Protocol (MRP) phase 1	459
MRP rings without shared interfaces	461
Ring initialization	462
How ring breaks are detected and healed	465
Master VLANs and customer VLANs in a topology group	466
Configuring MRP	467
Adding an MRP ring to a VLAN	468
Changing the hello and preforwarding times	469
MRP phase 2	469
Ring initialization for shared interfaces	471
How ring breaks Are detected and healed between shared interfaces	472
Selection of master node	472
RHP processing in rings with shared interfaces	473
Normal flow	473
Flow when a link breaks	474
Configuring MRP with shared interfaces	475
Using MRP diagnostics	476
Enabling MRP diagnostics	476
Displaying MRP diagnostics	476
Displaying MRP information	477
Displaying topology group information	477
Displaying ring information	478
MRP CLI example	479
Commands on switch A (master node)	480
Commands on switch B	480
Commands on switch C	481
Commands on switch D	481
Virtual Switch Redundancy Protocol (VSRP)	483
In this chapter	483
Overview of Virtual Switch Redundancy Protocol (VSRP)	483
Layer 2 and Layer 3 redundancy	485
Master election and failover	485
Configuring basic VSRP parameters	490
Enabling Layer 3 VSRP	491
Configuring optional VSRP parameters	491
Disabling VSRP on a VRID	491
Configuring authentication	491
Configuring a VRID IP address	492
VSRP fast start	493
Changing the backup priority	494
Saving the timer values received from the master	494
VSRP slow start	495
Changing the Time-To-Live (TTL)	495
Changing the hello interval	496
Changing the dead interval	496
Changing the backup hello state and interval	496
Changing the hold-down interval	497
Changing the default track priority	497
Specifying a track port	498
Disabling or re-enabling backup pre-emption	498
Port transition hold timer	498
Clearing VSRP information	499
VSRP and MRP signaling	499
Displaying VSRP information	501
Displaying VRID information	501
Displaying a summary of VSRP information	503
Displaying VSRP packet statistics for VSRP	504
Displaying the active interfaces for a VRID	505
Topology Groups	507
In this chapter	507

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999
1,000
1,001
1,002
1,003
1,004
1,005
1,006
1,007
1,008
1,009
1,010
1,011
1,012
1,013
1,014
1,015
1,016
1,017
1,018
1,019
1,020
1,021
1,022
1,023
1,024
1,025
1,026
1,027
1,028
1,029
1,030
1,031
1,032
1,033
1,034
1,035
1,036
1,037
1,038
1,039
1,040
1,041
1,042
1,043
1,044
1,045
1,046
1,047
1,048
1,049
1,050
1,051
1,052
1,053
1,054
1,055
1,056
1,057
1,058
1,059
1,060
1,061
1,062
1,063
1,064
1,065
1,066
1,067
1,068
1,069
1,070
1,071
1,072
1,073
1,074
1,075
1,076
1,077
1,078
1,079
1,080
1,081
1,082
1,083
1,084
1,085
1,086
1,087
1,088
1,089
1,090
1,091
1,092
1,093
1,094
1,095
1,096
1,097
1,098
1,099
1,100
1,101
1,102
1,103
1,104
1,105
1,106
1,107
1,108
1,109
1,110
1,111
1,112
1,113
1,114
1,115
1,116
1,117
1,118
1,119
1,120
1,121
1,122
1,123
1,124
1,125
1,126
1,127
1,128
1,129
1,130
1,131
1,132
1,133
1,134
1,135
1,136
1,137
1,138
1,139
1,140
1,141
1,142
1,143
1,144
1,145
1,146
1,147
1,148
1,149
1,150
1,151
1,152
1,153
1,154
1,155
1,156
1,157
1,158
1,159
1,160
1,161
1,162
1,163
1,164
1,165
1,166
1,167
1,168
1,169
1,170
1,171
1,172
1,173
1,174
1,175
1,176
1,177
1,178
1,179
1,180
1,181
1,182
1,183
1,184
1,185
1,186
1,187
1,188
1,189
1,190
1,191
1,192
1,193
1,194
1,195
1,196
1,197
1,198
1,199
1,200
1,201
1,202
1,203
1,204
1,205
1,206
1,207
1,208
1,209
1,210
1,211
1,212
1,213
1,214
1,215
1,216
1,217
1,218
1,219
1,220
1,221
1,222
1,223
1,224
1,225
1,226
1,227
1,228
1,229
1,230
1,231
1,232
1,233
1,234
1,235
1,236
1,237
1,238
1,239
1,240
1,241
1,242
1,243
1,244
1,245
1,246
1,247
1,248
1,249
1,250
1,251
1,252
1,253
1,254
1,255
1,256
1,257
1,258
1,259
1,260
1,261
1,262
1,263
1,264
1,265
1,266
1,267
1,268
1,269
1,270
1,271
1,272
1,273
1,274
1,275
1,276
1,277
1,278
1,279
1,280
1,281
1,282
1,283
1,284
1,285
1,286
1,287
1,288
1,289
1,290
1,291
1,292
1,293
1,294
1,295
1,296
1,297
1,298
1,299
1,300
1,301
1,302
1,303
1,304
1,305
1,306
1,307
1,308
1,309
1,310
1,311
1,312
1,313
1,314
1,315
1,316
1,317
1,318
1,319
1,320
1,321
1,322
1,323
1,324
1,325
1,326
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1,328
1,329
1,330
1,331
1,332
1,333
1,334
1,335
1,336
1,337
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1,341
1,342
1,343
1,344
1,345
1,346
1,347
1,348
1,349
1,350
1,351
1,352
1,353
1,354
1,355
1,356
1,357
1,358
1,359
1,360
1,361
1,362
1,363
1,364
1,365
1,366
1,367
1,368
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1,370
1,371
1,372
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1,377
1,378
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1,381
1,382
1,383
1,384
1,385
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1,387
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1,389
1,390
1,391
1,392
1,393
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1,395
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1,398
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1,400
1,401
1,402
1,403
1,404
1,405
1,406
1,407
1,408
1,409
1,410
1,411
1,412
1,413
1,414
1,415
1,416
1,417
1,418
1,419
1,420
1,421
1,422
1,423
1,424
1,425
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1,427
1,428
1,429
1,430
1,431
1,432
1,433
1,434
1,435
1,436

Match case Limit results 1 per page

BigIron RX Series Configuration Guide

783

53-1001810-01

Enabling next-hop recursion

Example when recursive route lookups are enabled

When recursive next-hop lookups are enabled, the device recursively looks up the next-hop

gateways along the route until the device finds an IGP route to the BGP route’s destination. Here is

an example.

The first lookup results in an IBGP route, to network 102.0.0.0/24.

Since the route to 102.0.0.1/24 is not an IGP route, the device cannot reach the next hop through

IP, and thus cannot use the BGP route. In this case, since recursive next-hop lookups are enabled,

the device next performs a lookup for 102.0.0.1’s next-hop gateway, 10.0.0.1.

The next-hop IP address for 102.0.0.1 is not an IGP route, which means the BGP route’s destination

still cannot be reached through IP.

The recursive next-hop lookup feature performs a lookup on

10.0.0.1’s next-hop gateway:

This lookup results in an IGP route.

In fact, this route is a directly-connected route.

As a result, the

BGP route’s destination is now reachable through IGP, which means the BGP route is eligible for

installation in the IP route table.

Here is the BGP route in the IP route table.

BigIron RX# show ip bgp route

Total number of BGP Routes: 5

Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED

H:HISTORY I:IBGP L:LOCAL M:MULTIPATH S:SUPPRESSED

Prefix

Next Hop

Metric

LocPrf

Weight Status

0.0.0.0/0

10.1.0.2

100

AS_PATH: 65001 4355 701 80

102.0.0.0/24

10.0.0.1

100

AS_PATH: 65001 4355 1

104.0.0.0/24

10.1.0.2

100

AS_PATH: 65001 4355 701 1 189

240.0.0.0/24

102.0.0.1

100

AS_PATH: 65001 4355 3356 7170 1455

250.0.0.0/24

209.157.24.1

100

AS_PATH: 65001 4355 701

BigIron RX# show ip route 102.0.0.1

Total number of IP routes: 38

Network Address

Gateway

Port

Cost

Type

102.0.0.0

10.0.0.1

1/1

AS_PATH: 65001 4355 1

BigIron RX# show ip bgp route 102.0.0.0

Number of BGP Routes matching display condition : 1

Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED

H:HISTORY I:IBGP L:LOCAL M:MULTIPATH S:SUPPRESSED

Prefix

Next Hop

Metric

LocPrf

Weight Status

102.0.0.0/24

10.0.0.1

100

AS_PATH: 65001 4355 1

BigIron RX# show ip route 10.0.0.1

Total number of IP routes: 38

Network Address

Gateway

Port

Cost

Type

10.0.0.0

0.0.0.0

1/1

AS_PATH: 65001 4355 1

BigIron RX# show ip route 240.0.0.0/24

Total number of IP routes: 38

Network Address

Gateway

Port

Cost

Type

240.0.0.0

10.0.0.1

1/1

AS_PATH: 65001 4355 1