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BGP Multihoming

Today I have been playing with configuring BGP and multihoming. I configured a simple test environment where one customer router (local AS 100) connects to two ISP routers from the same ISP (remote AS 200). I configure some kind of load-sharing amongst the two links to the ISP.

Important when configuring BGP is the concept to not becoming some kind of Transit AS for other BGP connections. It is also very important to secure your own router from accepting the whole routing table of the ISP. In this example I only accept a default route from the ISP.

I configured the following scenario:

The next section show the significant configuration of the different network components in the scenario.

ICTIVITY

interface Loopback0
 description INTERNAL NETWORK
 ip address 172.16.100.1 255.255.254.0
!
interface FastEthernet0/0
 description CONNECTION TO ISP-A
 ip address 192.168.1.1 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/1
 description CONNECTION TO ISP-B
 ip address 192.168.2.1 255.255.255.0
 duplex auto
 speed auto
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 bgp dampening
 network 172.16.100.0 mask 255.255.254.0
 timers bgp 1 5
 neighbor 192.168.1.2 remote-as 200
 neighbor 192.168.1.2 prefix-list DEFAULT-ONLY in
 neighbor 192.168.2.2 remote-as 200
 neighbor 192.168.2.2 prefix-list DEFAULT-ONLY in
 maximum-paths 2
 no auto-summary
!
ip prefix-list DEFAULT-ONLY seq 10 permit 0.0.0.0/0

ISP-A

interface FastEthernet0/0
 description CONNECTION TO ICTIVITY
 ip address 192.168.1.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/1
 description CONNECTION TO DEFAULT GATEWAY
 ip address 10.11.0.2 255.255.0.0
 duplex auto
 speed auto
!
router bgp 200
 no synchronization
 bgp log-neighbor-changes
 network 10.11.0.0 mask 255.255.0.0
 neighbor 192.168.2.1 remote-as 100
 neighbor 192.168.2.1 default-originate
 no auto-summary
!
ip route 0.0.0.0 0.0.0.0 10.11.0.1

ISP-B

interface FastEthernet0/0
 description CONNECTION TO ICTIVITY
 ip address 192.168.2.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/1
 description CONNECTION TO DEFAULT GATEWAY
 ip address 10.10.0.2 255.255.0.0
 duplex auto
 speed auto
!
router bgp 200
 no synchronization
 bgp log-neighbor-changes
 network 10.10.0.0 mask 255.255.0.0
 neighbor 192.168.2.1 remote-as 100
 neighbor 192.168.2.1 default-originate
 no auto-summary
!
ip route 0.0.0.0 0.0.0.0 10.10.0.1

The above configuration is very basic, but yet very powerful. The command ip prefix-list DEFAULT-ONLY seq 10 permit 0.0.0.0/0 assures that only default routes are accepted from the ISP. The routing table of ICTIVITY has the following entries:

Gateway of last resort is 192.168.1.2 to network 0.0.0.0

     172.16.0.0/23 is subnetted, 1 subnets
C       172.16.100.0 is directly connected, Loopback0
C    192.168.1.0/24 is directly connected, FastEthernet0/0
C    192.168.2.0/24 is directly connected, FastEthernet0/1
B*   0.0.0.0/0 [20/0] via 192.168.1.2, 00:00:24
               [20/0] via 192.168.2.2, 00:00:11

Looking at the routing table our router has two default routes for load-balancing and fail-over purposes.

RADIUS Authentication

I am sure that many of you would like to do the same thing and many of you successfully configured it. I am trying to configure RADIUS Authentication on my Cisco 877W. I have two different RADIUS policies, the first for privilege level 1 and the second for privilege level 15. I am using Microsoft IAS as RADIUS server.

I configured two policies and the second policy has the following Advanced Options set.

This means that the user should get privilege level 15, when logging in. I configured the following on the Cisco877W router.

aaa authentication login AD group radius local none
aaa authorization exec AD group radius
!
radius-server host 10.10.1.1 auth-port 1812 acct-port 1813 key 7 KEY
radius-server retry method reorder
radius-server transaction max-tries 2
radius-server timeout 4
radius-server deadtime 2
radius-server vsa send authentication
!
line vty 0 4
session-timeout 5
access-class 10 in
exec-timeout 5 0
login authentication AD
transport preferred none
transport input ssh
transport output telnet ssh

The user doesn’t get the privilege level 15, but comes in privilege level 1 and has to enter enable to get into privilege level 15. I turned on RADIUS debugging and I see the shell code coming by, as the debug output below shows.

%SSH-5-SSH2_SESSION: SSH2 Session request from 10.10.1.103 (tty = 1)
using crypto cipher ‘aes256-cbc’, hmac ‘hmac-sha1′ Succeeded
RADIUS/ENCODE(00000716): ask “Password: ”
RADIUS/ENCODE(00000716): send packet; GET_PASSWORD
RADIUS/ENCODE(00000716):Orig. component type = EXEC
RADIUS/ENCODE(00000716): dropping service type,
“radius-server attribute 6 on-for-login-auth” is off
RADIUS(00000716): Config NAS IP: 0.0.0.0
RADIUS/ENCODE(00000716): acct_session_id: 1814
RADIUS(00000716): sending
RADIUS/ENCODE: Best Local IP-Address 10.10.1.1 for Radius-Server 10.10.1.5
RADIUS(00000716): Send Access-Request to 10.10.1.5:1812 id 1645/31, len 81
RADIUS: authenticator 72 D9 B5 F1 76 72 9A D1 – 73 D7 E8 AF 21 F3 B5 0F
RADIUS: User-Name [1] 6 “rene”
RADIUS: User-Password [2] 18 *
RADIUS: NAS-Port [5] 6 3
RADIUS: NAS-Port-Id [87] 6 “tty3″
RADIUS: NAS-Port-Type [61] 6 Virtual [5]
RADIUS: Calling-Station-Id [31] 13 “10.10.1.103″
RADIUS: NAS-IP-Address [4] 6 10.10.1.1
RADIUS: Received from id 1645/31 10.10.1.5:1812, Access-Accept, len 83
RADIUS: authenticator BB BF B5 FD 1D 36 67 9B – FE 5A EE 5A 6C 42 5E B9
RADIUS: Vendor, Cisco [26] 25
RADIUS: Cisco AVpair [1]
19 “shell:priv-lvl=15″
RADIUS: Service-Type [6]
6 Login [1]
RADIUS: Class [25] 32
RADIUS: 3C 09 04 AE 00 00 01 37
00 01 0A 0A 01 05 01 C8 [< ??????7????????]
RADIUS: A6 C0 C2 0D FD 4C 00
00 00 00 00 00 00 13 [?????L????????]
RADIUS(00000716): Received from id 1645/31
%SEC_LOGIN-5-LOGIN_SUCCESS: Login Success
[user: rene] [Source: 10.10.1.103] [localport: 22]

I am running out of options. I have tried to use the Cisco-AVpair in IAS, but no success. I tried using only Telnet, but no success. Maybe someone has an option to try…

Network simulator

More often I have to change critical configuration options in live environments, but sometimes I don’t no the effect of these changes on the network. So I would like to build a test network where I can check the impact of the configuration changes. A good network simulator would definitely help in this situation.

Cisco switches use IOS software and software always contains bugs. A new release can contain bug fixes, but also new features. It could be useful to test these new features in a test environment. Unfortunately we and our customers don’t have a lot of routers and switches in spare. So I need a network simulator, which can simulate real Cisco IOS software.

First I used the tool Dynamips / Dynagen. This text Cisco router emulator emulates a couple of Cisco routers. The tool helps by loading different images on your own laptop. The hard part of Dynamips is the configuration of a test environment. All configuration is done in text files, with a lot of different options.

Luckily I found a graphical user interface for Dynamips. It is called GNS3. I really love this tool, because designing a network environment is dragging and dropping some routers, define the desired modules and connect them together. Next start the emulator and you are ready to go. The new version of GNS3 doesn’t only emulate routers, but also the Cisco PIX firewall with software version 8.x. Of course it is no Cisco ASA, but better something then nothing.

I really recommend this tool to everybody involved with network infrastructures and especially Cisco environments. The tool can help you by testing features like routing protocols and QoS tools. GNS3 is also very useful when studying for a Cisco Exam, even for the CCIE certification.

Cisco IOS and macro’s

Today I had to remotely configure some layer 3 Cisco Catalyst 3560 switches.

LDAP and eSafe Gateway

eSafe Gateway can be used for scanning incoming and outgoing SMTP connections for virusses and SPAM. Normally eSafe Gateway doesn’t check incoming mail addresses against a directory like Active Directory or Novell Directory Services.

This means that all mail addresses for a trusted domain are forwarded to the internal mail server. In the most ideal situation unknown mail addresses should be blocked at the eSafe Gateway. This feature will take away load off the internal mail server, because this mail server doesn’t have to generate NDR (Non-Delivery Reports) messages. Beside that, the eSafe Gateway also doesn’t have to process the NDR’s. LDAP (Lightweight Directory Access Protocol) provides this functionality.

With LDAP configured, the eSafe Gateway will synchronize all known mail objects from the directory services with the eSafe Gateway. By this, the eSafe Gateway knows all valid mail objects and can block invalid mail objects. There are some issues when configuring a LDAP query with Active Directory. By default Active Directory only allows 1000 objects in one query. Some customers have more mail object, so this settings needs to be added. Inside Active Directory, you should edit the LDAP Policy setting MaxPageSize. Look here for more information about editing the MaxPageSize variable.

Some organizations use PublicFolders in conjunction with Microsoft. These PublicFolders can be mail-enabled and should be added in the LDAP filter configuration inside eSafe Gateway. This is done by changing the default filter

(&(|(objectClass=person)(objectClass=contact)(objectClass=organizationalPerson))(!(objectClass=computer)))

in

(&(|(objectClass=person)(objectClass=contact)(objectClass=organizationalPerson)(objectClass=publicFolder))(!(objectClass=computer)))

This results in adding the mail object PublicFolder to the LDAP query.