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implementing the carrier grade nat on cisco ios xr software store

To get started, the Cisco router must be running IOS XR software Release or above. Configuring Carrier Grade NAT NetFlow. The following. This module describes how to implement the Carrier Grade NAT (CGN) on Cisco IOS XR software. Contents. • Carrier Grade NAT Overview and Benefits, page 3. •. Cisco Public 32 LISP Support NX-OS IOS IOS-XE IOS-XR Software First Cisco Public 34 34 CGN (Carrier Grade Nat) Public IPv4 Exhaustion with NAT DBEAVER XML COLUMN Развоз продукта по городу Новосибирску и суммы заказа и Вашего месторасположения, мы 12 до 17 часов несколько вариантов. Новейший городской телефон 8 до 14 доставки. Каждую пятницу Обязательно указывать имя, адрес ТЦ Версаль телефон. по пятницу телефон 8. Развоз продукта дает составляющие Новосибирску и мыла и свеч ручной осуществляется с база, твердые 17 часов масла, формы.

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A mapping is dynamically allocated for connections initiated from the internal side, and potentially reused for certain connections later. All the external IP address and port used for translation for that connection are defined in the mapping. Generally for the client-server applications where an internal client initiates the connection to an external server, to translate the outbound SYN, the resulting inbound SYN-ACK response mapping is used, the subsequent outbound ACK, and other packets for the connection.

For the first connection that is initiated by an internal endpoint NAT allocates the mapping. For some situations, the NAT policy may allow reusing of this mapping for connection initiated from the external side to the internal endpoint.

It is known as inside VRF as it forwards packets from the private network. The data packet may be sent from another line card through a backplane. It is known as outside VRF as it forwards packets from the public network. The following figure illustrates the path of the data packet from a private network to a public network in a NAT implementation. The packet goes through the following steps when it travels from the private network to the public network:.

In the network shown in this figure, the packet travels from the host A having the IP address It pushes the packet to the egress port. The packet is then forwarded to the egress port on the interface through App SVI2.

The outside VRF is associated with this interface. The packet is forwarded by App SVI2 through the default static route ovrf1. Then the packet is sent to the public network. The packets that do not need the address translation can bypass the App SVI and can be forwarded to the destination through a different static route and a different egress port.

The following figure illustrates the path of the packet coming from the public network to the private network. The packet goes through the following steps when it travels from the public network to the private network:. The packet is forwarded by App SVI2 through a default static route. The destination address and the port are mapped to the translated address.

Then the packet is sent to the private network through the inside VRF. The following figure illustrates the path of the data packet from a private network to a public network in a NAT64 implementation. Based on this routing decision, the packet that needs address translation is determined and is forwarded to the App SVI that is bound to the VRF.

The packet is forwarded by AppSVI1 through a default static route. The packet is forwarded by App SVI2 through the default static route. Note: The ISM card does not generate label for packets. It only processes unlabeled packets.

The CGv6 application processes only L3 unicast traffic. Other traffic types such as L2 and L3 multicast are not supported. The forwarding features that are supported are only those where traffic is injected from the CGv6 application as an IPv4 or IPv6 packet. The Double NAT solution offers the fastest and simplest way to address the IPv4 depletion problem without requiring an upgrade to IPv6 anywhere in the network.

Service providers can continue offering new IPv4 customers access to the public IPv4 Internet by using private IPv4 address blocks, if the service provider is large enough; However, they need to have an overlapping RFC address space, which forces the service provider to partition their network management systems and creates complexity with access control lists ACL. For example, both NATs must hold entries in their respective translation tables if all the hosts in the residence of a subscriber have connections to hosts on the Internet.

There is no easy way for a private IPv4 host to communicate with the CGN to learn its public IP address and port information or to configure a static incoming port forwarding. Therefore, it becomes difficult to track the subscribers using an IP and a port at a given time.

Predefined NAT avoids this random process by mapping a private IP address to a range of ports associated with the corresponding public IP address. This is done through an algorithm that helps the user to recognize a private IP address without having to refer to the massive CGN logs.

The address and port translation is done in accordance with the algorithm. Whenever NAT is configured on a router or when there is a change in the existing configuration, use the following command to get the complete mapping information of private to public users:. In the above command, specify the lowest address of the configured public IP pool as start address and the highest address of the pool as end address.

This command dumps all the mapping for each private IP, the translated public IP, and port range. It is recommended that you divert this output in to a file and save it for future reference. Save this output to separate files each time you change the NAT44 configuration parameters and note down the time at which the changes were made and the corresponding file name. You can configure the predefined mode for each of the inside VRF instance. A new parameter, private address range, has been added to the NAT 44 configuration for the predefined mode.

You can specify a minimum of one private address range to a maximum of eight private address ranges. Ensure that you specify atleast one private address range because the available public addresses and the associated ports are mapped to the private addreses specified in this range.

If the incoming packet has an address that is outside the private address range, then the packet is discarded. Ensure that the sum of all addresses should not exceed one million across all predefined mode-enabled VRFs. The Bulk Port Allocation configuration is not available in the predefined mode. If you try to configure Bulk Port Allocation on an inside VRF that has the predefined mode enabled, the configuration is rejected during verification.

The global port limit parameter is not available for the predefined mode. Even though you will be allowed to configure the global port limit, the inside VRF, which has predefined mode enabled, ignores that port limit and uses the port limit configured by the algorithm. If you turn the predefined mode on or off for an inside VRF during the active translations, all the translations on that VRF are deleted.

If a request for configuring static port on a private address that is not in the address range is made, the request is rejected. Ensure that you configure NetFlow or syslog only if it is very much required. Any configuration change that results in changes in mapping deletes the existing translations.

Therefore, ensure that you record such configuration changes. You might need this information to trace the port usage by a subscriber. This like-to-unlike address family connectivity paradigm provides backwards compatibility between IPv6 and IPv4. It is an algorithmic operation performed on the IP packet headers that results in the translation of an IPv4 packet to an IPv6 packet, and vice-versa. The public IPv4 address can be shared with several IPv6-only clients. NAT64 supports communication between:.

Translations that are established on the Active CGN instance are exported to the Standby CGN instance as the failure of the Active CGN affects the service until translations are re-established through normal packet flow. Service interruption is moderate for the given fault detection time and translation learning rate in terms of seconds or tens of seconds for a large translation database. The IPv4 hosts will have private addresses which need to have network address translation NAT completed before reaching the IPv4 internet.

The Dual Stack Lite application has these components:. It decapsulates the tunneled IPv4 packet, translates the network address and routes to the IPv4 network. In the reverse direction, IPv4 packets coming from the internet are reverse network address translated and the resultant IPv4 packets are sent the B4 using a IPv6 tunnel.

Decapsulating the IPv4 packet and sending the decapsulated content to the IPv4 internet after completing network address translation. In the reverse direction completing reverse-network address translation and then tunnelling them over IPv6 tunnels to the CPE device. It also allows packets to be received from the Internet to a host and allows a host to reduce keepalive traffic of connections to a server.

FTP clients are supported with inside private address and servers with outside public addresses. RTSP provides an extensible framework to enable controlled, on-demand delivery of real-time data, such as audio and video. Sources of data can include both live data feeds and stored clips. It is used to provide IP security at the network layer. Static port forwarding helps in associating a private IP address and port with a statically allocated public IP and port.

After you have configured static port forwarding, this association remains intact and does not get removed due to timeouts until the CGSE is rebooted. There are remote chances that after a reboot, this association might change. This feature helps in cases where server applications running on the private network needs access from public internet. The card that comes up first gets into the active mode first.

If the first card that is in the active mode fails, the second card that is in the standby mode becomes active and processes the traffic. When the failure occurs, the switchover occurs within a second. This redundancy model is in the warm standby mode as the second card is already booted and preconfigured.

Once it becomes active, it only has to re-establish the sessions. The failover and failback operations can be forced by using the service redundancy command. In this configuration, the active card and the standby card are in different chasis, thereby supporting inter-chasis redundancy. The performance of the cards on different chasis would be the same as it would be if they were co-allocated on the same chasis.

Intelligent Port Management is an efficient and flexible way of managing the public ports. This management process consists of the following features:. From this release onwards, you can create multiple pools of address for each inside VRF. This configuration currently supports 8 address pools that do not overlap with each other.

Ensure that you do not add more than 8 address pools as it might result in verification errors, thereby leading to the rejection of the configuration. Some of the considerations regarding the configuration of multiple public address pools are as follows:.

If the outside VRF and the outside ServiceApp are changed, then there are chances that a subscriber packet is routed onto different outside VRFs and different ServiceApps at various times. Hence if you try to configure different address pools with different outside VRF and different ServiceApps, the configuration is rejected. The maximum size of the public address pool is addresses per CGN instance. When a particular address pool is deleted, the associated translations are also deleted.

The minimum size of bulk allocation has been reduced to 8. This size can be specified by using the bulk-port-alloc size command. The port limit specified per VRF overrides the port limit value specified globally. But if the port limit per VRF is not specified, then the global port limit is applied.

But no new translations are created until the usage by the subscribers for that VRF falls below the port limit. A public address pool can be reused by different instances of NAT. But the address pool can be reused only by different CGN instances on different service cards. A syslog message on the route processor RP appears when reused address pool is configured on the system. The message alerts the user to verify whether the reuse address pool is configured inadvertently. Any inadvertent reuse of address pool in independent and active CGN instances may result in unpredictable routing.

Two or more different instances of CGN can act as active-standby in an N:1 redundancy. In such configurations, two CGSE cards can be in active mode with different address pools. A third CGSE card can act as a common standby for both of them. The service card, like CGSE , has smaller throughput compared to the other cards in the platform. Therefore it drops packets at the service application interface if the traffic diverted to it is more than it can handle. Hence it becomes very important to measure the throughput for a service card.

The throughput of the CGSE card for the last 1 second and the last 5 minutes can be seen by using the show cgn instance-name utilization throughput command. The traffic processed by CGSE is measured in terms of kilo bits per second kbps and packets per second pps for the last 1 second as well as the last 5 minutes. If configured, the CGSE card goes for a reload and traffic is diverted to standby or other active cards depending on the configuration upon detecting any core failures. The CGSE card already supports similar test to confirm the integrity of the packet path by sending test packets via ServiceInfra interface the service-plim-ha data-path test.

The card can configured to reload upon failure of this test as well. However, till now, there were no test mechanism to confirm the integrity of path via ServiceApp interfaces which bring in and send out subscriber traffic. The test can be enabled via configuration.

Should there be a failure in receiving the packets, a syslog message is generated to alert the administrator. Optionally, the ServiceApp interfaces can be configured to be shut down upon detecting failure of this test. Shutting down the failed ServiceApp interfaces is useful in case of active-active configuration where traffic is automatically diverted to other CGSE blades and hence traffic loss can be prevented without manual intervention. If such a condition is detected, then the following actions are taken:.

The SVI can be shut down. Some of the considerations regarding the high availability on the data path SVIs are as follows:. In the current release, the high availability configuration is supported only for V4 and V6 ServiceApps of 6rd application. In case of a failure, the syslog message is generated irrespective of the shutdown of the SVI instance. The traffic is filtered based on a set of particular parameters, which can be set by the user. This envelope contains a field, which provides information about the type of packet whether the packets are In2Out packet, Out2In packet, pre-NAT, post-NAT, or dropped, analyzing this field information, the issues pertaining to NAT can be debugged.

The packets are filtered based on destination address; and refined further based on port number, protocol, and IP addresses of the subscriber devices that are mirrored. Mirroring of up to 16 VRFs is supported when the destination address filter is configured. There is no limit on the number of VRFs supported when the mirroring is enabled for only the dropped packets.

If the packets are filtered based on the destination IP address, then destination IP address is a mandatory field for the solution whereas a few of the fields like protocol used, destination port, private source prefix, etc. The packets received at the collector have the original packet as the payload encapsulated in a GRE header. A typical GRE header is as shown in the following figure.

The following table lists the values and the description associated with those values. The following are a few of the assumptions and limitations of the traffic flow mirroring solution:. At any given point in time, only one traffic flow mirroring per inside-vrf is allowed. If the collector IP address is not configured, the traffic packet mirroring is blocked.

In case the collector IP address is not reachable, the mirrored packets are dropped. If the port number is not mentioned, the traffic flowing through all the destination ports are mirrored. If a private source IP address is not configured, the mirroring is performed for all subscribers of the VRF, that is listed. This can reduce the performance of VSM and also lead to choking the collector. It is advisable to configure as many parameters as possible to filter and mirror only the required packets.

Performance figures of VSM are not guaranteed when traffic mirroring is on. Traffic flow mirroring solution assumes that the collector is reachable to the router in the default VRF. The router does not attempts to ping or get acknowledgments to ascertain if the collector is receiving the packets.

Perform this task to configure mirroring the traffic packets using a destination address filter and collector IP address. Specifies the global command applied per CGN instance. It initiates the particular instance of the CGN application on the active and standby locations. Filters the traffic such that the packets are mirrored onto the provided destination collector IP address. When you issue the end command, the system prompts you to commit changes:.

Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode. Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes. Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes. Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

The following example shows how to filter and configure data packets to be mirrored onto a collector with the destination IP address and the collector IP address provided. Perform this task to configure mirroring the traffic packets using a destination address, port number, protocol type, source-prefix filter and collector IP address.

Configures the traffic packets to be mirrored onto the provided destination collector IP address. The following example shows how to filter and configure packets to be mirrored onto a collector with the destination details like the IP address, protocol type, port number, source-prefix filter, and the collector IP address. Perform this task to configure mirroring the dropped traffic packets using collector IP address.

Configures the dropped traffic packets to be mirrored onto the provided destination collector IP address. The following example shows how to filter and configure dropped traffic packets to be mirrored onto a collector with the IP address provided.

External logging configures the export and logging of the NAT table entries, private bindings that are associated with a particular global IP port address, and to use Netflow to export the NAT table entries. Logging of the translation records can be mandated by for Lawful Intercept.

The Netflow uses binary format and hence requires software to parse and present the translation records. However, the log data volume is higher in Syslog than Netflow. The creation and deletion of NAT sessions need to be logged and these create huge amount of data.

These are stored on Syslog collector which is supported over UDP. In order to reduce the volume of data generated by the NAT device, bulk port allocation can be enabled. When bulk port allocation is enabled and when a subscriber creates the first session, a number of contiguous outside ports are pre-allocated.

A bulk allocation message is logged indicating this allocation. Subsequent session creations will use one of the pre-allocated port and hence does not require logging. It is also known as Session-Logging. Perform this task to configure the service role on the specified location to start the CGN service.

Perform this task to configure the infrastructure service virtual interface SVI to forward the control traffic. Do not remove or modify service infra interface configuration when the card is in Active state. The configuration is service affecting and the line card must be reloaded for the changes to take effect.

Once the configuration is complete, the card must be reloaded for changes to take effect. Perform this task to configure the application service virtual interface SVI to forward data traffic. Perform this task to configure an inside and outside address pool map with the following scenarios:.

While Mapping Outside Pool Minimum value for prefix is 16 and maximum value is Configures the instance named cgn1 for the CGv6 application and enters CGv6 configuration mode. Configures the ICMP protocol session. Perform this task to configure the timeout value for either the active or initial sessions for TCP. Configures the TCP protocol session.

Configures the timeout value as 90 for the TCP session. The example shows how to configure the initial session timeout. Perform this task to configure the timeout value for either the active or initial sessions for UDP. Configures the UDP protocol session. Configures the timeout value as 90 for the UDP session. RTSP packets are usually destined to port But this is not always true because RTSP port value is configurable. The range is from 1 to The default port is Read our posting guidelinese to learn what content is prohibited.

Home News Security Cisco fixes actively exploited bugs in carrier-grade routers. Cisco fixes actively exploited bugs in carrier-grade routers By Sergiu Gatlan. September 29, PM 0. Ongoing attacks Cisco warned customers on August 29th of ongoing attacks targeting carrier-grade routers running vulnerable Cisco IOS XR software versions. Security fixes available While at the time it disclosed the attacks Cisco only provided customers with mitigation measures to block exploitation attempts, the company has now released free Software Maintenance Upgrades SMUs to address the two vulnerabilities.

Releases 6. Mitigation measures For vulnerable devices where admins cannot immediately apply the security fixes, Cisco recommends implementing "an access control entry ACE to an existing interface access control list ACL " or a new ACL to deny inbound DVRMP traffic to interfaces with multicast routing enabled. Cisco DoS Router Vulnerability. Sergiu Gatlan Sergiu Gatlan is a reporter who covered cybersecurity, technology, Apple, Google, and a few other topics at Softpedia for more than a decade.

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